I am using \mathbf{} for include bold symbols in my equation. It works fine with all symbols with the exception of \iota. I tried to use equation environment and to exclude subindex. The following is my writing:

    \mathbf{Y}=\rho \mathbf{WY}+\alpha \mathbf{\iota}_{N}+\mathbf{X\beta}+\mathbf{WX\theta}+\mathbf{u},\label{eqgeneral1}\\ 
    \mathbf{u}=\lambda\mathbf{Wu}+\mathbf{\varepsilon}  \label{eqgeneral2}

I obtain this:

I want this:

¿How can I solve this?

  • It's not just iota though? It's all of the Greek letters right, and there's a very good reason for that. \mathbf{} and the standard LaTeX font applies to Roman letters only, not Greek letters, not symbols like + - =, nothing like that. Try: tex.stackexchange.com/questions/595/… – Au101 Aug 30 '18 at 19:29
  • 1
    You can use \bm or \boldsymbol. – Bernard Aug 30 '18 at 19:44
  • For new documents, I would recommend loading unicode-math instead of legacy font packages. Any Unicode math font is going to come with bold math symbols. You can use them with \symbf{\iota} or \mathbf{\iota}. It’s also possible to do more complex things, such as using a different font for your Greek alphabet. – Davislor Aug 31 '18 at 2:30
  • If you’re forced to use pdflatex, you might try the isomath package, which supports a large number of Greek math alphabets. You can also use a LGR-encoded legacy Greek font with mathastext. – Davislor Aug 31 '18 at 2:31

Thanks to user Au101. I used \boldsymbol and it works for me:

    \mathbf{Y}=\rho \mathbf{WY}+\alpha \boldsymbol{\iota}_{N}+\mathbf{X\beta}+\mathbf{WX\theta}+\mathbf{u},\label{eqgeneral1}\\ 
    \mathbf{u}=\lambda\mathbf{Wu}+\mathbf{\varepsilon}  \label{eqgeneral2}

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