# Undefined Control Sequence error in tikz [duplicate]

I want to write a commutative diagram with tikz where some arrows are labeled with matrices. How can I improve the diagram to look correct, because the matrices look not correct in the diagram? Here is my work. and I want to do as in the picture.

$\begin{tikzcd} b \arrow[r, "{\begin{pmatrix} \mu \\ -\pi \end{pmatrix}}"] \arrow[equal]{d} & c\oplus d \arrow[r, "{\begin{pmatrix} \rho & \sigma \end{pmatrix}}"] \arrow[equal]{d} & e \arrow[r, "\lambda \nu"] \arrow[d, "\Phi"] & {b[1]} \arrow[equal]{d} \\ b \arrow[r, "{\begin{pmatrix} \mu \\ -\pi \end{pmatrix}}"'] & c\oplus d \arrow[r, "{\begin{pmatrix} \rho & \sigma^\prime \end{pmatrix}}"'] & e \arrow[r, "\lambda \nu"'] & {b[1]} \end{tikzcd}$


I keep getting the following logs: undefined control sequences. Please can someone tell me what is wrong with my code?

• Welcome! Please post a minimal, complete example that we can compile. See minimal working example (MWE) Feb 13 at 11:51
• you have posted an identical question here. Please try to create a viable example; re-posting the same does not help you nor us. Feb 13 at 12:01
• This question looks pretty much identical to your earlier question tex.stackexchange.com/q/633696/35864. Please do not ask the same question twice in short succession. Instead edit and improve your question following the comments you got. In particular consider turning the code snippet into a valid document (with \documentclass a preamble loading the required packages and \begin{document}...\end{document}). Feb 13 at 12:02
• you have not even said what command was undefined, presumably you have loaded tikz-cd (although you do not show that) but pmatrix is not defined by default, when asking abiut a error always provide a file which reproduces the error and show the exact error message fron the log Feb 13 at 12:22