| name | mermaid-diagram |
| description | Generates diagrams (probability trees, flowcharts, sequence diagrams) using Mermaid CLI (mmdc), exports them as PNG, and returns the relative path for embedding in LaTeX via latex-illustrator. Use whenever a diagram would be cleaner as a Mermaid chart than as raw TikZ. |
Mermaid Diagram
When to use this skill
Use instead of TikZ when the diagram is:
- Árbol de probabilidad (probability tree with branches and multiplied values)
- Diagrama de flujo de un proceso o algoritmo
- Diagrama de secuencia o de estados
- Any tree/hierarchy that would require complex TikZ positioning
Keep using TikZ for: Venn diagrams, boxplots, histograms, coordinate-based plots. TikZ is better when you need precise geometric control.
Tool Requirements
Check availability before running:
which mmdc
If missing: npm install -g @mermaid-js/mermaid-cli or it may be at ~/.local/bin/mmdc.
Also needed for PNG → LaTeX embedding: \usepackage{graphicx} in the LaTeX preamble (handled by latex-writer).
Execution Protocol
Step 1 — Write the .mmd file
Write the Mermaid source to a temporary file. Choose the diagram type that fits:
Árbol de probabilidad (graph LR):
graph LR
R(( )) -->|"P(A) = 0.53"| A(( ))
R -->|"P(B) = 0.47"| B(( ))
A -->|"0.47"| AC["P(C) = 0.47 × 0.53 = 0.2491"]
A -->|"0.09"| AD["P(D) = 0.09 × 0.53 = 0.0477"]
B -->|"0.12"| BC["P(C) = 0.12 × 0.47 = 0.0564"]
B -->|"0.45"| BD["P(D) = 0.45 × 0.47 = 0.2115"]
style A fill:#fff,stroke:#333
style B fill:#fff,stroke:#333
style R fill:#fff,stroke:#333
Tips for árbol de probabilidad:
- Root and intermediate nodes:
(( )) for circles
- Leaf nodes:
["text"] for rectangles showing the product
- Edge labels:
|"P(X|Y) = val"| — use quotes to allow special chars
- Direction:
LR (left to right) works best for probability trees
- Keep leaf text short: just the product, e.g.
"0.47 × 0.53 = 0.2491"
Step 2 — Generate PNG
mmdc -i {input.mmd} -o {output_dir}/figures/{name}.png \
-w 900 -H 500 --backgroundColor white
-w and -H: width and height in pixels. Adjust for the number of branches.
- 2-branch tree:
-w 800 -H 350
- 3-branch tree per node:
-w 900 -H 500
- 4+ branches:
-w 1000 -H 650
--backgroundColor white: ensures clean white background for embedding- Output goes into
{root}/output/figures/ so the path is clean relative to the .tex
Verify output:
ls -lh {output_dir}/figures/{name}.png
Step 3 — Embed in LaTeX
Pass to latex-illustrator (or write directly if called standalone):
\begin{figure}[H]
\centering
\includegraphics[width=0.82\textwidth]{figures/{name}.png}
\end{figure}
Width guidelines:
- Simple 2-level tree:
0.65\textwidth
- 3-level tree (root → 2 nodes → 3 leaves each):
0.82\textwidth
- Very wide tree:
\textwidth
The figures/ path is relative to the .tex file — ensure both live in the same output/ directory.
LaTeX Preamble Requirements
The LaTeX document must have:
\usepackage{graphicx}
\usepackage{float}
latex-writer includes these by default.
Common Mermaid Patterns
Árbol de probabilidad total (Bayes setup)
graph LR
R(( )) -->|"P(H₁)"| H1(( ))
R -->|"P(H₂)"| H2(( ))
H1 -->|"P(E|H₁)"| E1["P(H₁)·P(E|H₁)"]
H1 -->|"P(Eᶜ|H₁)"| Ec1["P(H₁)·P(Eᶜ|H₁)"]
H2 -->|"P(E|H₂)"| E2["P(H₂)·P(E|H₂)"]
H2 -->|"P(Eᶜ|H₂)"| Ec2["P(H₂)·P(Eᶜ|H₂)"]
Flowchart de decisión
graph TD
A[Inicio] --> B{¿n > 30?}
B -->|Sí| C[Usar Z]
B -->|No| D{¿σ conocida?}
D -->|Sí| C
D -->|No| E[Usar t con n-1 gl]
Constraints
- No usar para Venn, boxplot, histograma — esos van en TikZ.
- Siempre fondo blanco (
--backgroundColor white) para que el PNG integre limpio en el PDF.
- El PNG va en
output/figures/ — nunca directamente en output/ para mantener el directorio limpio.
- No editar el PNG — si el diagrama queda mal, regenerar el
.mmd y volver a compilar.
- Registrar el bug de
\fi: en TikZ, nunca usar \fi, \else, \if como nombres de variables en \foreach — son primitivas TeX reservadas. Usar \fabs, \fval, \fnum, etc.
