From eacd9962911f8be2ce456aa29ba9a1b008430ae8 Mon Sep 17 00:00:00 2001
From: Bram Spanoghe <70662421+bspanoghe@users.noreply.github.com>
Date: Wed, 18 Mar 2026 16:35:46 +0100
Subject: [PATCH 1/6] Update MCMC_1-intro.jl

- use `generated_quantities` instead of calling model
- minor clarification
---
 .../solved_notebooks/P5_mcmc/MCMC_1-intro.jl    | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/exercises/solved_notebooks/P5_mcmc/MCMC_1-intro.jl b/exercises/solved_notebooks/P5_mcmc/MCMC_1-intro.jl
index 02c6944..f907b2a 100644
--- a/exercises/solved_notebooks/P5_mcmc/MCMC_1-intro.jl
+++ b/exercises/solved_notebooks/P5_mcmc/MCMC_1-intro.jl
@@ -199,9 +199,6 @@ mutation_model = mutations(times);
 # ╔═╡ d4dbc185-6087-4862-b6e5-b5e4f51c2866
 md"And can then generate random samples of the output as we are used to:"
 
-# ╔═╡ 8b0bf05f-92a0-4ce7-8042-08c790088688
-mutation_model() # random sample of N
-
 # ╔═╡ 3e4998e7-4981-4945-8bf2-ddb5afcb43b1
 chain = sample(mutation_model, Prior(), 2000);
 
@@ -211,6 +208,9 @@ chain = sample(mutation_model, Prior(), 2000);
 # ╔═╡ a9d54dfc-5337-412f-86b0-deeb5a0b6928
 histogram(α_sp, title = "Sample of prior of α")
 
+# ╔═╡ fdec279a-a7e3-4a57-a3f1-183e22558725
+generated_quantities(mutation_model, chain) # random samples of N
+
 # ╔═╡ 425b4b6c-76b8-4676-8d0a-fd26711400d6
 md"### Inference"
 
@@ -240,8 +240,12 @@ md"""
 We can verify that for our conditioned model, the value of `N` has been set as constant: 
 """
 
+# ╔═╡ 31d48207-4432-4d8f-a18a-40f01d4a0a6c
+# ╠═╡ show_logs = false
+conditioned_chain = sample(conditioned_model, Prior(), 5);
+
 # ╔═╡ d03cef36-3e82-4de4-89e7-af9f772edd8d
-conditioned_model() # always returns `observed_mutations`
+generated_quantities(conditioned_model, conditioned_chain) # always returns `observed_mutations`
 
 # ╔═╡ 371a48d5-daea-4d0b-968b-7e3056a65494
 md"""
@@ -320,7 +324,7 @@ md"""
 To answer how old the ancestral seahorse fossil is, we need to update the model a little.
 So far the fossil ages were considered to be known exactly and given as input to the model `ts`. Since the seahorse fossil's age is unknown, we add a parameter for it called `fossil_age`. 
 
-As prior knowledge we can use the fact that it must have evolved _after_ the ray-finned fish fossil (30 Ma after weird old fish), but _before_ modern seahorses (450 Ma after the bony fish fossil).
+As prior knowledge we can use the fact that it must have evolved _after_ the ray-finned fish fossil (30 Ma after the bony fish fossil), but _before_ modern seahorses (450 Ma after the bony fish fossil).
 """
 
 # ╔═╡ fd15afe1-72d7-4663-b2b6-afa0dd219db8
@@ -428,10 +432,10 @@ end
 # ╟─31378eb3-51a5-4ad6-a713-7f77c7ceafcc
 # ╠═48f6b7dc-13aa-4057-8468-97db047773ba
 # ╟─d4dbc185-6087-4862-b6e5-b5e4f51c2866
-# ╠═8b0bf05f-92a0-4ce7-8042-08c790088688
 # ╠═3e4998e7-4981-4945-8bf2-ddb5afcb43b1
 # ╠═3421987d-1aab-4cab-bf83-dd3653715bce
 # ╟─a9d54dfc-5337-412f-86b0-deeb5a0b6928
+# ╠═fdec279a-a7e3-4a57-a3f1-183e22558725
 # ╟─425b4b6c-76b8-4676-8d0a-fd26711400d6
 # ╟─b8adbdd4-2642-4375-9979-0cb8f52c5bc8
 # ╠═70f9e94d-a4e6-47d6-8d19-b60f7011d572
@@ -439,6 +443,7 @@ end
 # ╟─2d0c969d-03a2-4e4c-ace4-e439f81c771b
 # ╠═a35a43e2-e6b0-47ce-80b2-48148336274c
 # ╟─c5f0dbb3-fba1-41f2-b7d2-740012603555
+# ╠═31d48207-4432-4d8f-a18a-40f01d4a0a6c
 # ╠═d03cef36-3e82-4de4-89e7-af9f772edd8d
 # ╟─371a48d5-daea-4d0b-968b-7e3056a65494
 # ╠═0d2c1359-434f-4f3d-8c04-c452c46d7ae8

From ed272ca48dd422cdea908befbd7f722a871749c1 Mon Sep 17 00:00:00 2001
From: Bram Spanoghe <70662421+bspanoghe@users.noreply.github.com>
Date: Thu, 19 Mar 2026 14:14:23 +0100
Subject: [PATCH 2/6] update intro plots

---
 .../solved_notebooks/P5_mcmc/MCMC_1-intro.jl  | 23 ++++++++++---------
 1 file changed, 12 insertions(+), 11 deletions(-)

diff --git a/exercises/solved_notebooks/P5_mcmc/MCMC_1-intro.jl b/exercises/solved_notebooks/P5_mcmc/MCMC_1-intro.jl
index f907b2a..340d70d 100644
--- a/exercises/solved_notebooks/P5_mcmc/MCMC_1-intro.jl
+++ b/exercises/solved_notebooks/P5_mcmc/MCMC_1-intro.jl
@@ -136,12 +136,11 @@ We can sample some values from this prior distribution and use them to plot the
 
 # ╔═╡ 1080294d-8da9-4326-a53b-afe158dc2ab9
 begin
-	scatter(times, observed_mutations, xlabel = "Time (My)",
-		ylabel = "Number of mutations", label = false, xlims = (0, 500), 
-		ylims = (0, 400), title = "A priori relationship between t and mean N"
-	);
-	for α in rand(prior_alpha, 1000)
-		plot!(x -> α*x, color = :purple, alpha = 0.05, label = false);
+	plot(xlabel = "Time (My)", ylabel = "Number of mutations", xlims = (0, 500),
+		 	ylims = (0, 400), title = "A priori relationship between t and mean N");
+	scatter!(times, observed_mutations, label = "Cyt C", color = :deeppink);
+	for α in rand(prior_alpha, 200)
+		plot!(x -> α*x, color = :dodgerblue, alpha = 0.3, label = false);
 	end
 	plot!()
 end
@@ -295,11 +294,13 @@ md"Plotting some sampled mutation rates from this distribution onto our data sho
 
 # ╔═╡ 87e70d5a-7a45-4a3e-b6c4-a894cc78621b
 begin
-	scatter(times, observed_mutations, xlabel = "Time (My)",
-		ylabel = "Number of mutations", label = false, xlims = (0, 500), 
-		ylims = (0, 400), title = "A posteriori relationship between t and mean N"
-	);
-	plot!([x -> αᵢ*x for αᵢ in alpha_samples[1:10:end]], color = :purple, opacity = 0.1, label = false)
+	plot(xlabel = "Time (My)", ylabel = "Number of mutations", xlims = (0, 500),
+		 	ylims = (0, 400), title = "A posteriori relationship between t and mean N");
+	for α in alpha_samples[1:10:end]
+		plot!(x -> α*x, color = :dodgerblue, alpha = 0.1, label = false);
+	end
+	scatter!(times, observed_mutations, label = "Cyt C", color = :deeppink);
+	plot!()
 end
 
 # ╔═╡ 87059440-2919-4f6d-9d32-0df3ce75e2a2

From 0893cfbf21e584a8bca62630f50b3366786e1996 Mon Sep 17 00:00:00 2001
From: bspanoghe <bram.spanoghe@gmail.com>
Date: Sun, 22 Mar 2026 22:58:28 +0100
Subject: [PATCH 3/6] give less of the answer in student notebooks

---
 .../P5_mcmc/MCMC_2-basics.jl                  | 62 ++++---------------
 .../P5_mcmc/MCMC_3-advanced.jl                | 33 ++--------
 2 files changed, 17 insertions(+), 78 deletions(-)

diff --git a/exercises/student_notebooks/P5_mcmc/MCMC_2-basics.jl b/exercises/student_notebooks/P5_mcmc/MCMC_2-basics.jl
index e49044f..c4e93eb 100644
--- a/exercises/student_notebooks/P5_mcmc/MCMC_2-basics.jl
+++ b/exercises/student_notebooks/P5_mcmc/MCMC_2-basics.jl
@@ -1,5 +1,5 @@
 ### A Pluto.jl notebook ###
-# v0.20.4
+# v0.20.21
 
 using Markdown
 using InteractiveUtils
@@ -62,7 +62,7 @@ md"### 2: Unconditional expected value of Y"
 
 # ╔═╡ 3decb2ec-210a-4b2f-842d-6fd40dd3f77b
 @model function mole()
-	X ~ X_prior
+	X ~ missing
 	Y ~ missing
 	return Y
 end
@@ -108,11 +108,8 @@ md"### 5: Conditional distribution of X (with more data)"
 
 # ╔═╡ b2b16c34-e12a-4bea-8098-313d01913bbf
 @model function mole2()
-	X ~ X_prior
-	Ys = missing
-	for i in missing
-		Ys[i] ~ missing
-	end
+	X ~ missing
+	# how to deal with a vector of values again...
 end
 
 # ╔═╡ 26a245d2-c5b6-484d-bdf7-541948ff06ad
@@ -233,11 +230,7 @@ md"### 3: Conditional expected value"
 
 # ╔═╡ 126d3954-c77d-4c98-abe0-fd87d14e6265
 @model function lights()
-	μ ~ lights_prior
-	lifespans = missing
-	for i in missing
-		lifespans[i] ~ missing
-	end
+	missing
 end
 
 # ╔═╡ 37bf6ca5-e42b-406e-94d6-bcd1e706e2bd
@@ -314,21 +307,9 @@ len_obs = [94.0, 88.7, 89.6, 69.8, 52.8, 84.0, 89.3, 66.4, 95.1, 81.6]
 
 # ╔═╡ b15de91a-fc48-4cdc-a35f-6453a9a59982
 @model function fishmixture()
-	fs1 ~ missing # fraction of species 1
-	fishlendist = missing
-	
-	fishlens = missing
-	for i in missing
-		fishlens[i] ~ fishlendist
-	end
+	missing
 end
 
-# ╔═╡ 94a9e163-f7c0-4d22-8d37-5641bc49eb6b
-fishmodel = missing
-
-# ╔═╡ 40d460d2-1f2b-4d33-ba74-9a9d1e48f9ec
-fishchain = missing # don't forget to plot to check convergence
-
 # ╔═╡ 819ed364-4bc9-43ec-aa50-b965c8f1c826
 fs1_est = missing
 
@@ -337,18 +318,6 @@ md"### 3🌟: Conditional expected value (spicy)"
 
 # ╔═╡ 8629d049-b9fd-4e9e-9b55-401a3069e956
 @model function fishmixture🌟()
-	fs1 ~ missing # fraction of species 1
-	
-	fishlens = missing
-	isspecies1 = missing
-	for i in missing
-		isspecies1[i] ~ missing
-		if isspecies1[i] == 1.0
-			fishlens[i] ~ missing
-		else
-			fishlens[i] ~ missing
-		end
-	end
 end
 
 # ╔═╡ 483cbe4d-64d3-4b16-b6fc-e97b21f174a6
@@ -418,26 +387,19 @@ md"### 1: All points"
 # ╔═╡ 84d27c98-9513-4ae3-8101-621c083a1b01
 @model function circle(σ=0.25)
 	# generate a circle center
-	xC ~ missing
-	yC ~ missing
+	missing
 	
 	# generate a radius
-	R ~ missing
+	missing
 	
 	# three random points in polar coordinates
-	θ1 ~ missing
-	θ2 ~ missing
-	θ3 ~ missing
 	
 	# P1
-	x1 ~ Normal(missing, σ)
-	y1 ~ Normal(missing, σ)
+	missing
 	# P2
-	x2 ~ Normal(missing, σ)
-	y2 ~ Normal(missing, σ)
+	missing
 	# P3
-	x3 ~ Normal(missing, σ)
-	y3 ~ Normal(missing, σ)
+	missing
 end
 
 # ╔═╡ 543c40d5-e8a7-492d-a0b8-e7e73e5953e2
@@ -572,8 +534,6 @@ end
 # ╟─8e030a06-5104-4c5b-b1f2-f86464e66502
 # ╠═6ebf3a16-0e6a-491f-8280-b4327ed52cf0
 # ╠═b15de91a-fc48-4cdc-a35f-6453a9a59982
-# ╠═94a9e163-f7c0-4d22-8d37-5641bc49eb6b
-# ╠═40d460d2-1f2b-4d33-ba74-9a9d1e48f9ec
 # ╠═819ed364-4bc9-43ec-aa50-b965c8f1c826
 # ╟─952a941a-8703-45a3-aac1-a290a181e8c5
 # ╠═8629d049-b9fd-4e9e-9b55-401a3069e956
diff --git a/exercises/student_notebooks/P5_mcmc/MCMC_3-advanced.jl b/exercises/student_notebooks/P5_mcmc/MCMC_3-advanced.jl
index a1b6c7e..e548399 100644
--- a/exercises/student_notebooks/P5_mcmc/MCMC_3-advanced.jl
+++ b/exercises/student_notebooks/P5_mcmc/MCMC_3-advanced.jl
@@ -1,5 +1,5 @@
 ### A Pluto.jl notebook ###
-# v0.20.4
+# v0.20.21
 
 using Markdown
 using InteractiveUtils
@@ -7,7 +7,7 @@ using InteractiveUtils
 # This Pluto notebook uses @bind for interactivity. When running this notebook outside of Pluto, the following 'mock version' of @bind gives bound variables a default value (instead of an error).
 macro bind(def, element)
     #! format: off
-    quote
+    return quote
         local iv = try Base.loaded_modules[Base.PkgId(Base.UUID("6e696c72-6542-2067-7265-42206c756150"), "AbstractPlutoDingetjes")].Bonds.initial_value catch; b -> missing; end
         local el = $(esc(element))
         global $(esc(def)) = Core.applicable(Base.get, el) ? Base.get(el) : iv(el)
@@ -86,12 +86,7 @@ md"""
 
 # ╔═╡ 70fd793a-3ce3-446f-adc1-65ce0a68e48a
 @model function cars(ts)
-	t_switch ~ missing
-	σ ~ missing
-	
-	for pointidx in 1:length(ts)
-		missing
-	end
+	missing
 end
 
 # ╔═╡ fb202b86-c058-4f03-9062-ab282c71d5c4
@@ -132,19 +127,11 @@ logistic(t, P0, r, K) =  K / (1 + (K - P0)/P0 * exp(-r*t))
 md"### 1"
 
 # ╔═╡ f080f708-a457-40a3-936c-b82d5159975d
-dropletdist = MixtureModel([Poisson(10), Poisson(30)], [0.75, 0.25]);
+dropletdist = missing
 
 # ╔═╡ 7b4aef69-10ec-4935-b7fd-4c1d49aa9b3d
 @model function petrigrowth()
-	P0 ~ dropletdist
-    r ~ LogNormal(0.0, 0.3)
-	K ~ Normal(1e5, 1e4)
-
-	logfun = t -> logistic(t, P0, r, K)
-	Pt = missing
-    P_obs ~ missing
-	
-    return logfun
+	missing
 end
 
 # ╔═╡ 3e98c640-4bb0-4b5d-bae0-769133a599a7
@@ -171,15 +158,7 @@ end
 
 # ╔═╡ d9b50958-20ae-4085-80d6-19420c7d89df
 @model function petrigrowth🌟()
-	P0 ~ dropletdist🌟
-    r ~ LogNormal(0.0, 0.3)
-	K ~ Normal(1e5, 1e4)
-
-	logfun = t -> logistic(t, P0, r, K)
-	Pt = missing
-    P_obs ~ missing
-	
-    return logfun
+	missing
 end
 
 # ╔═╡ 0704ed4d-5b3e-401d-a496-98782cb20b09

From 58c9dee4fafb41208a803b1bdd8b1e86f3ef9bba Mon Sep 17 00:00:00 2001
From: bspanoghe <bram.spanoghe@gmail.com>
Date: Sun, 22 Mar 2026 23:00:41 +0100
Subject: [PATCH 4/6] Update MCMC_2-basics.jl

ironically, add missing `missing`
---
 exercises/student_notebooks/P5_mcmc/MCMC_2-basics.jl | 1 +
 1 file changed, 1 insertion(+)

diff --git a/exercises/student_notebooks/P5_mcmc/MCMC_2-basics.jl b/exercises/student_notebooks/P5_mcmc/MCMC_2-basics.jl
index c4e93eb..0d7e7cb 100644
--- a/exercises/student_notebooks/P5_mcmc/MCMC_2-basics.jl
+++ b/exercises/student_notebooks/P5_mcmc/MCMC_2-basics.jl
@@ -318,6 +318,7 @@ md"### 3🌟: Conditional expected value (spicy)"
 
 # ╔═╡ 8629d049-b9fd-4e9e-9b55-401a3069e956
 @model function fishmixture🌟()
+	missing
 end
 
 # ╔═╡ 483cbe4d-64d3-4b16-b6fc-e97b21f174a6

From 21c2421632d1472cc9028fe71c3aa6b736e87052 Mon Sep 17 00:00:00 2001
From: Bram Spanoghe <70662421+bspanoghe@users.noreply.github.com>
Date: Mon, 23 Mar 2026 11:38:37 +0100
Subject: [PATCH 5/6] transfer changes of intro notebook to student version

---
 .../student_notebooks/P5_mcmc/MCMC_1-intro.jl | 44 +++++++++++--------
 1 file changed, 25 insertions(+), 19 deletions(-)

diff --git a/exercises/student_notebooks/P5_mcmc/MCMC_1-intro.jl b/exercises/student_notebooks/P5_mcmc/MCMC_1-intro.jl
index 22a26a9..340d70d 100644
--- a/exercises/student_notebooks/P5_mcmc/MCMC_1-intro.jl
+++ b/exercises/student_notebooks/P5_mcmc/MCMC_1-intro.jl
@@ -1,5 +1,5 @@
 ### A Pluto.jl notebook ###
-# v0.20.4
+# v0.20.21
 
 using Markdown
 using InteractiveUtils
@@ -136,12 +136,11 @@ We can sample some values from this prior distribution and use them to plot the
 
 # ╔═╡ 1080294d-8da9-4326-a53b-afe158dc2ab9
 begin
-	scatter(times, observed_mutations, xlabel = "Time (My)",
-		ylabel = "Number of mutations", label = false, xlims = (0, 500), 
-		ylims = (0, 400), title = "A priori relationship between t and mean N"
-	);
-	for α in rand(prior_alpha, 1000)
-		plot!(x -> α*x, color = :purple, alpha = 0.05, label = false);
+	plot(xlabel = "Time (My)", ylabel = "Number of mutations", xlims = (0, 500),
+		 	ylims = (0, 400), title = "A priori relationship between t and mean N");
+	scatter!(times, observed_mutations, label = "Cyt C", color = :deeppink);
+	for α in rand(prior_alpha, 200)
+		plot!(x -> α*x, color = :dodgerblue, alpha = 0.3, label = false);
 	end
 	plot!()
 end
@@ -199,9 +198,6 @@ mutation_model = mutations(times);
 # ╔═╡ d4dbc185-6087-4862-b6e5-b5e4f51c2866
 md"And can then generate random samples of the output as we are used to:"
 
-# ╔═╡ 8b0bf05f-92a0-4ce7-8042-08c790088688
-mutation_model() # random sample of N
-
 # ╔═╡ 3e4998e7-4981-4945-8bf2-ddb5afcb43b1
 chain = sample(mutation_model, Prior(), 2000);
 
@@ -211,6 +207,9 @@ chain = sample(mutation_model, Prior(), 2000);
 # ╔═╡ a9d54dfc-5337-412f-86b0-deeb5a0b6928
 histogram(α_sp, title = "Sample of prior of α")
 
+# ╔═╡ fdec279a-a7e3-4a57-a3f1-183e22558725
+generated_quantities(mutation_model, chain) # random samples of N
+
 # ╔═╡ 425b4b6c-76b8-4676-8d0a-fd26711400d6
 md"### Inference"
 
@@ -233,15 +232,19 @@ md"""
 """
 
 # ╔═╡ a35a43e2-e6b0-47ce-80b2-48148336274c
-# forgot_comma = mutation_model | (N = observed_mutations) 
+# forgot_comma = mutation_model | (N = observed_mutations)
 
 # ╔═╡ c5f0dbb3-fba1-41f2-b7d2-740012603555
 md"""
 We can verify that for our conditioned model, the value of `N` has been set as constant: 
 """
 
+# ╔═╡ 31d48207-4432-4d8f-a18a-40f01d4a0a6c
+# ╠═╡ show_logs = false
+conditioned_chain = sample(conditioned_model, Prior(), 5);
+
 # ╔═╡ d03cef36-3e82-4de4-89e7-af9f772edd8d
-conditioned_model() # always returns `observed_mutations`
+generated_quantities(conditioned_model, conditioned_chain) # always returns `observed_mutations`
 
 # ╔═╡ 371a48d5-daea-4d0b-968b-7e3056a65494
 md"""
@@ -291,11 +294,13 @@ md"Plotting some sampled mutation rates from this distribution onto our data sho
 
 # ╔═╡ 87e70d5a-7a45-4a3e-b6c4-a894cc78621b
 begin
-	scatter(times, observed_mutations, xlabel = "Time (My)",
-		ylabel = "Number of mutations", label = false, xlims = (0, 500), 
-		ylims = (0, 400), title = "A posteriori relationship between t and mean N"
-	);
-	plot!([x -> αᵢ*x for αᵢ in alpha_samples[1:10:end]], color = :purple, opacity = 0.1, label = false)
+	plot(xlabel = "Time (My)", ylabel = "Number of mutations", xlims = (0, 500),
+		 	ylims = (0, 400), title = "A posteriori relationship between t and mean N");
+	for α in alpha_samples[1:10:end]
+		plot!(x -> α*x, color = :dodgerblue, alpha = 0.1, label = false);
+	end
+	scatter!(times, observed_mutations, label = "Cyt C", color = :deeppink);
+	plot!()
 end
 
 # ╔═╡ 87059440-2919-4f6d-9d32-0df3ce75e2a2
@@ -320,7 +325,7 @@ md"""
 To answer how old the ancestral seahorse fossil is, we need to update the model a little.
 So far the fossil ages were considered to be known exactly and given as input to the model `ts`. Since the seahorse fossil's age is unknown, we add a parameter for it called `fossil_age`. 
 
-As prior knowledge we can use the fact that it must have evolved _after_ the ray-finned fish fossil (30 Ma after weird old fish), but _before_ modern seahorses (450 Ma after the bony fish fossil).
+As prior knowledge we can use the fact that it must have evolved _after_ the ray-finned fish fossil (30 Ma after the bony fish fossil), but _before_ modern seahorses (450 Ma after the bony fish fossil).
 """
 
 # ╔═╡ fd15afe1-72d7-4663-b2b6-afa0dd219db8
@@ -428,10 +433,10 @@ end
 # ╟─31378eb3-51a5-4ad6-a713-7f77c7ceafcc
 # ╠═48f6b7dc-13aa-4057-8468-97db047773ba
 # ╟─d4dbc185-6087-4862-b6e5-b5e4f51c2866
-# ╠═8b0bf05f-92a0-4ce7-8042-08c790088688
 # ╠═3e4998e7-4981-4945-8bf2-ddb5afcb43b1
 # ╠═3421987d-1aab-4cab-bf83-dd3653715bce
 # ╟─a9d54dfc-5337-412f-86b0-deeb5a0b6928
+# ╠═fdec279a-a7e3-4a57-a3f1-183e22558725
 # ╟─425b4b6c-76b8-4676-8d0a-fd26711400d6
 # ╟─b8adbdd4-2642-4375-9979-0cb8f52c5bc8
 # ╠═70f9e94d-a4e6-47d6-8d19-b60f7011d572
@@ -439,6 +444,7 @@ end
 # ╟─2d0c969d-03a2-4e4c-ace4-e439f81c771b
 # ╠═a35a43e2-e6b0-47ce-80b2-48148336274c
 # ╟─c5f0dbb3-fba1-41f2-b7d2-740012603555
+# ╠═31d48207-4432-4d8f-a18a-40f01d4a0a6c
 # ╠═d03cef36-3e82-4de4-89e7-af9f772edd8d
 # ╟─371a48d5-daea-4d0b-968b-7e3056a65494
 # ╠═0d2c1359-434f-4f3d-8c04-c452c46d7ae8

From 537eb293a848c4b9762b695ebf177b9051506481 Mon Sep 17 00:00:00 2001
From: Bram Spanoghe <70662421+bspanoghe@users.noreply.github.com>
Date: Mon, 23 Mar 2026 14:31:35 +0100
Subject: [PATCH 6/6] improved example solutions

- fit more to previous practical
- add more explanation
---
 .../solved_notebooks/P5_mcmc/MCMC_2-basics.jl | 56 +++++++++++--------
 .../P5_mcmc/MCMC_3-advanced.jl                | 22 +++++---
 .../solved_notebooks/P5_mcmc/MCMC_4-review.jl | 16 +++++-
 3 files changed, 59 insertions(+), 35 deletions(-)

diff --git a/exercises/solved_notebooks/P5_mcmc/MCMC_2-basics.jl b/exercises/solved_notebooks/P5_mcmc/MCMC_2-basics.jl
index 99aeb62..9b46eac 100644
--- a/exercises/solved_notebooks/P5_mcmc/MCMC_2-basics.jl
+++ b/exercises/solved_notebooks/P5_mcmc/MCMC_2-basics.jl
@@ -5,6 +5,7 @@ using Markdown
 using InteractiveUtils
 
 # ╔═╡ 94c6f31d-1a43-4221-b60c-1fa0ef8738b8
+# ╠═╡ show_logs = false
 using Pkg; Pkg.activate("..")
 
 # ╔═╡ 45bc5b66-c81b-4afb-8a7e-51aff9609c62
@@ -70,8 +71,11 @@ end
 # ╔═╡ 76dd814d-0d9b-4f7e-aff8-990da57d052b
 molemodel = mole()
 
+# ╔═╡ 611575ef-20ee-4731-9b5d-3fec90d8b038
+molechain = sample(molemodel, Prior(), 2000)
+
 # ╔═╡ b5bd5114-0a0c-4aa3-af00-4f3d05edc5e3
-Y_samples = [molemodel() for i in 1:2000];
+Y_samples = molechain[:Y];
 
 # ╔═╡ 4e8b9000-cb61-4f01-9ba9-17276ad0335e
 E_Y = mean(Y_samples)
@@ -83,7 +87,7 @@ md"### 3: Conditional expected value of X"
 cond_mole = molemodel | (Y = 3,);
 
 # ╔═╡ 014538da-b5ef-41c8-b799-2c000b4c9134
-molechain = sample(cond_mole, NUTS(), 2000);
+molechain_cond = sample(cond_mole, NUTS(), 2000);
 
 # ╔═╡ b02dc714-e2bb-4ae2-acf9-c37a4389f953
 plot(molechain)
@@ -95,7 +99,7 @@ X_samplescondY = molechain[:X];
 E_XcondY = mean(molechain[:X])
 
 # ╔═╡ 5521933a-a42e-4a67-94b9-84eab52ddf07
-E_X = mean(X_prior)
+E_X = mean(Exponential(100))
 
 # ╔═╡ ca3e730c-a940-4c76-93eb-70ae4aa0e008
 md"### 4: Conditional distribution of X"
@@ -107,9 +111,9 @@ histogram(molechain[:X])
 md"### 5: Conditional distribution of X (with more data)"
 
 # ╔═╡ b2b16c34-e12a-4bea-8098-313d01913bbf
-@model function mole2()
+@model function mole2(n)
 	X ~ Exponential(100)
-	Ys = zeros(4)
+	Ys = zeros(n)
 	for i in 1:length(Ys)
 		Ys[i] ~ Uniform(0, X)
 	end
@@ -119,7 +123,7 @@ end
 Y_obs = [3.0, 1.5, 0.9, 5.7]
 
 # ╔═╡ 2f5c14e9-709a-40ec-a6cb-ddd870cc1a60
-mole_cond2 = mole2() | (Ys = Y_obs,)
+mole_cond2 = mole2(4) | (Ys = Y_obs,)
 
 # ╔═╡ 7f90e18d-9af8-42fa-984b-aaa7c8c458b5
 molechain2 = sample(mole_cond2, NUTS(), 2000);
@@ -174,7 +178,7 @@ histogram(potato_chain[:N])
 md"### 2: Probability"
 
 # ╔═╡ 9dd6fa35-37d5-4ab4-ac2c-f4eefdabadd2
-p_potato1 = mean(potato_chain[:N] .> 6 .&& potato_chain[:W] .> 175)
+p_potato1 = mean((potato_chain[:N] .> 6) .&& (potato_chain[:W] .> 175))
 
 # ╔═╡ 989b755b-2275-4aae-a3e2-3b107a72fc0b
 md"### 3: Probability (with more data)"
@@ -283,23 +287,27 @@ md"""
 """
 
 # ╔═╡ 8fc58fa4-b005-4f32-9eae-a8143582a1ae
-@model function lights_censored(time_observed, n_working)
+@model function lights_censored(time_observed)
 	μ ~ LogNormal(log(40), 0.5)
-	
+
+	# we still have lifespan information for 2 lights
 	lifespans = zeros(2)
 	for i in 1:length(lifespans)
 		lifespans[i] ~ Exponential(μ)
 	end
-	p_stillworking = 1 - cdf(Exponential(μ), time_observed)
-	n_working ~ Binomial(n_working + length(lifespans), p_stillworking) 
-		# or simply `2 ~ Binomial(4, p_stillworking)`
+
+	# use the information that 2 lights are still working
+	p_stillworking = 1 - cdf(Exponential(μ), time_observed) 
+		# probability that μ > 30_000 => this is the success rate for a lamp to still work after 30_000 hours
+	n_working ~ Binomial(4, p_stillworking) 
+		# the amount of lights still working (`n_workin`) follows a Binomial distribution: they can be seen as the successes of attempting to "not break" 4 times, each with the success rate for a lamp to still work after 30_000 hours
 end
 
 # ╔═╡ fe2958a7-e9dd-4eca-979d-a80df12f8735
-lightmodel_cens = lights_censored(30, 2) | (lifespans = [16, 20],)
+lightmodel_cens = lights_censored(30) | (lifespans = [16, 20], n_working = 2)
 
 # ╔═╡ 8abafb6a-dc83-422c-82d1-a721a0e1eca0
-lightschain_cens = sample(lightmodel_cens, MH(), 10_000)
+lightschain_cens = sample(lightmodel_cens, PG(10), 1_000)
 
 # ╔═╡ 5ba2886c-b2e1-49f4-90c6-549acc808f77
 plot(lightschain_cens)
@@ -381,12 +389,12 @@ md"### 3🌟: Conditional expected value (spicy)"
 	fs1 ~ Uniform(0, 1) # fraction of species 1
 	
 	fishlens = zeros(10)
-	isspecies1 = zeros(10)
+	isspecies1 = zeros(10) # for every fish: are you species 1?
 	for i in 1:length(fishlens)
-		isspecies1[i] ~ Bernoulli(fs1)
-		if isspecies1[i] == 1.0
+		isspecies1[i] ~ Bernoulli(fs1) # "are you species 1" is a binomial distr!
+		if isspecies1[i] == 1.0 # if species 1, length follows their distribution
 			fishlens[i] ~ Normal(90, 15)
-		else
+		else # otherwise length follows distribution of species 2
 			fishlens[i] ~ Normal(60, 10)
 		end
 	end
@@ -396,10 +404,10 @@ end
 fishmodel🌟 = fishmixture🌟() | (fishlens = len_obs,)
 
 # ╔═╡ bdb0d902-3056-43fb-abb0-15f2494fcf9d
-fishchain🌟 = sample(fishmodel🌟, PG(20), 2000)
+fishchain🌟 = sample(fishmodel🌟, MH(), 20_000) # PG convergences poorly without a lot of particles => takes a long time => to win time you can instead try the very fast (but inconsistent) `MH` with a criminally large amount of samples, just make sure to check convergence for this sampler!
 
 # ╔═╡ 7372c616-05a8-428d-ab04-a7be9f65653d
-plot(fishchain🌟)
+plot(fishchain🌟) # MH happened to work well this time! 🥳
 
 # ╔═╡ 40cc67c1-8627-4f1f-b135-a9770f916b53
 p_fish4_is_species1 = mean(fishchain🌟["isspecies1[4]"])
@@ -475,14 +483,15 @@ md"### 1: All points"
 	R ~ Uniform(0, 50)
 	
 	# three random points in polar coordinates
+	
+	# define angles (radius has already been chosen)
 	θ1 ~ Flat() 
-		# `Uniform(0, 2*pi)` is also possible but can get the sampler stuck
-		# at 0 or 2π!
+		# `Uniform(0, 2*pi)` is also possible but can get the sampler stuck at 0 or 2π! Another option here is a Uniform distribution with a very large domain, such as `Uniform(-1000, 1000)`
 	θ2 ~ Flat()
 	θ3 ~ Flat()
 	
 	# P1
-	x1 ~ Normal(xC + R * cos(θ1), σ)
+	x1 ~ Normal(xC + R * cos(θ1), σ) # wait, it's all trigonometry?
 	y1 ~ Normal(yC + R * sin(θ1), σ)
 	# P2
 	x2 ~ Normal(xC + R * cos(θ2), σ)
@@ -567,6 +576,7 @@ end
 # ╟─78eb7779-f182-4419-b5d8-79a2f5c5d6da
 # ╠═3decb2ec-210a-4b2f-842d-6fd40dd3f77b
 # ╠═76dd814d-0d9b-4f7e-aff8-990da57d052b
+# ╠═611575ef-20ee-4731-9b5d-3fec90d8b038
 # ╠═b5bd5114-0a0c-4aa3-af00-4f3d05edc5e3
 # ╠═4e8b9000-cb61-4f01-9ba9-17276ad0335e
 # ╟─8777b133-7d7c-4a85-b89c-2f00093e9984
diff --git a/exercises/solved_notebooks/P5_mcmc/MCMC_3-advanced.jl b/exercises/solved_notebooks/P5_mcmc/MCMC_3-advanced.jl
index 535159f..29cf6e3 100644
--- a/exercises/solved_notebooks/P5_mcmc/MCMC_3-advanced.jl
+++ b/exercises/solved_notebooks/P5_mcmc/MCMC_3-advanced.jl
@@ -17,6 +17,7 @@ macro bind(def, element)
 end
 
 # ╔═╡ 75581580-2fb2-4112-b397-2b775eb64630
+# ╠═╡ show_logs = false
 using Pkg; Pkg.activate("..")
 
 # ╔═╡ e07a1ae5-43b7-4c12-831d-43e1738eeac0
@@ -158,11 +159,14 @@ plot(dropletdist)
     r ~ LogNormal(0.0, 0.3)
 	K ~ Normal(1e5, 1e4)
 
-	logfun = t -> logistic(t, P0, r, K)
-	Pt = max(logfun(t_obs), 0) 
+	# model number of bacteria at time `t_obs`
+	num_bacteria = logistic(t_obs, P0, r, K)
+	num_bacteria = max(num_bacteria, 0) 
 		# set to 0 if negative to prevent possible errors (not required)
-    P_obs ~ Poisson(Pt)
-	
+    P_obs ~ Poisson(num_bacteria)
+
+	# to answer the questions, it's useful to return the growth through time as a function 
+	logfun = t -> logistic(t, P0, r, K)
     return logfun
 end
 
@@ -173,13 +177,13 @@ petrimodel = petrigrowth(5) | (P_obs = 21_000,)
 petrichain = sample(petrimodel, PG(40), 2_000)
 
 # ╔═╡ 9633f07a-d583-4680-b3cc-f5701540968f
-plot(petrichain)
+plot(petrichain) # convergence is not great unless you use a large number of particles (and even then it's not ideal)
 
 # ╔═╡ 7d0e5f0b-2cdf-4946-a186-f70774e363bb
-logfuns = generated_quantities(petrimodel, petrichain);
+logfuns = generated_quantities(petrimodel, petrichain); # it's easy here to get a function describing growth through time because we returned it in our model!
 
 # ╔═╡ c642574c-c01b-4398-aac9-43e514d7fa25
-petri_samples = [logfun(8.0) for logfun in logfuns]
+petri_samples = [logfun(8.0) for logfun in logfuns] # get population sizes at t = 8
 
 # ╔═╡ d15fa091-839c-4239-96e2-eaf7335ce620
 prob_splittable = mean((petri_samples .>= 1e4) .&& (petri_samples .<= 1e5))
@@ -188,7 +192,7 @@ prob_splittable = mean((petri_samples .>= 1e4) .&& (petri_samples .<= 1e5))
 md"### 2"
 
 # ╔═╡ 3d9b73ef-2aae-4c19-bddc-4081927ec92d
-plot(logfuns[1:10:1000], xlims = (0, 12), legend = false, color = :skyblue, alpha = 0.5)
+plot(logfuns, xlims = (0, 12), legend = false, color = :skyblue, alpha = 0.1)
 
 # ╔═╡ 9ab88be4-4cf8-4747-ac36-3f1b82899be0
 md"### 3🌟"
@@ -200,7 +204,7 @@ dropletdist🌟 = MixtureModel(
 		truncated(Normal(30, sqrt(30)), lower = 0.0)
 	],
 	[0.75, 0.25]
-);
+); # Normal distributions are the Poisson distributions of the continuous world (make sure to match mean and variance of both distributions) - ideally also use `truncated` to ensure the normal distributions are positive
 
 # ╔═╡ 4e730df9-f619-464a-b8a3-57448132404b
 begin
diff --git a/exercises/solved_notebooks/P5_mcmc/MCMC_4-review.jl b/exercises/solved_notebooks/P5_mcmc/MCMC_4-review.jl
index 92488ad..279cd62 100644
--- a/exercises/solved_notebooks/P5_mcmc/MCMC_4-review.jl
+++ b/exercises/solved_notebooks/P5_mcmc/MCMC_4-review.jl
@@ -1,5 +1,5 @@
 ### A Pluto.jl notebook ###
-# v0.20.4
+# v0.20.21
 
 using Markdown
 using InteractiveUtils
@@ -57,15 +57,23 @@ md"""
 	Where is the hornet nest located? You may assume the nest is somewhere within the plot's boundaries, and the flight speed of a wasp is around 5 to 10 m/s.
 """
 
+# ╔═╡ 0ac905af-2798-41c2-8295-60e40f384f64
+v_prior = LogNormal(log(8), 0.5) 
+	# or something else positive with a peak around 5-10
+
+# ╔═╡ 9bc4efa9-5e4c-41d5-86cb-997fb0788ea0
+plot(v_prior, xlims = (0, 20)) # seems about right!
+
 # ╔═╡ ac0496d3-aa62-4c07-8233-16fe67c52b24
 @model function horenaars(xs, ys, ts)
+	σ ~ Exponential(10)
     x_nest ~ Uniform(0, 1000)
     y_nest ~ Uniform(0, 1000)
-    v_wasp ~ Gamma(8) # or something similar
+    v_wasp ~ LogNormal(log(8), 0.5)
 
     for i in 1:length(ts)
 		dist = sqrt((xs[i] - x_nest)^2 + (ys[i] - y_nest)^2)
-        ts[i] ~ Normal(2*dist / v_wasp, 10)
+        ts[i] ~ Normal(2*dist / v_wasp, σ)
     end
 end
 
@@ -103,6 +111,8 @@ end
 # ╠═c1850e64-9e2c-46fb-b7cd-22e8af81d3aa
 # ╟─28cb3363-6856-4164-b60e-36ec2e88ed56
 # ╟─484b56ec-57b2-496d-a5cf-1b1c0da97c58
+# ╠═0ac905af-2798-41c2-8295-60e40f384f64
+# ╠═9bc4efa9-5e4c-41d5-86cb-997fb0788ea0
 # ╠═ac0496d3-aa62-4c07-8233-16fe67c52b24
 # ╠═88e95234-4e43-4ead-bd0f-f32f9fc109c2
 # ╠═c5a94b3e-a4b8-42e6-a8c7-79e942212852