\geqslant Undefined control sequence in Latex - latex

When I compile the following latex code:
\begin{align}
f_{m}(x) = c_{1,m} \times I(x_{i}^{m} \geqslant t_{m} ) + c_{2,m} \times I(x_{i}^{m} < t_{m} ),
\end{align}
I always get an error:
! Undefined control sequence.
<argument> ..._{1,m} \times I(x_{i}^{m} \geqslant
t_{m} ) + c_{2,m} \times I...
l.124 \end{align}
When I replace \geqslant with >=, it is okay.
I already include the amsmath package. What would cause the problem?
Thanks and regards!

That command isn't defined in the amsmath package, but rather the amssymb package -- put \usepackage{amssymb} in your preamble and you should be fine.

Related

latex ambiguous warning while compiling with MikTex

I'm compiling LaTeX with MiKTeX. I get an ambiguous warning which interrupts compilation.
LaTeX Warning: Command \' invalid in math mode on input line 209.
209 > \begin{equation} M = \left\{ m : {R_n} \left[ a \right] \right\} \end{equation}
The same line compiles very well on Overleaf.
You may wish to try replacing \{ and \} in this instance with \lbrace and \rbrace - this should compile properly. So your equation becomes
M = \left\lbrace m : {R_n} \left[ a \right] \right\rbrace

How to number gathered equations using single number

I want to number gathered equations, but single number for several equations. Following is the code I've used. But it results numbering both equations. I want to equations to be justified, not right aligned. Spilt and align environment right align the equations. Is there any way to do this?
\begin{gather}
\eta_{c1} P_{pv}(k) + \eta_{c2} P_{bat}(k) \leq P_{conG,rate} \\\
P_{grid} + P_{load} \geq -P_{conG,rate}
\end{gather}
After \ you can put \nonumber this way you can avoid having both equations numbered
As said by Good Luck, you can add \nonumber at the end of the line before \\.
A problem I encountered was that when adding a \label{label_name} the Eq.~\ref{label_name} showed as (for example) Eq.2.5 instead of Eq.2. I've managed to sort this by moving the \label{label_name} to the row below \begin{gather}. So for example my code would look like this:
\begin{gather}
\label{labe_name}
e=\sum_{n=0}^{\infty}{\frac{1}{n!}}\\
\begin{aligned}
&\textit{\small Where:}\nonumber\\
&\textit{\small $1^{st}$ line and more explanations to fill the line} \nonumber\\
&\textit{\small $2^{nd}$ line}\nonumber\\
&\textit{\small ext \dots}\nonumber\\
\end{aligned}
\end{gather}
Make sure to have this packages:
\usepackage{amsmath,amssymb}
Here is a cleaner solution than using \nonumber. Using gathered or aligned environments inside an equation environment groups the equations and assigns one number to them. This is recommended by the amsmath user guide.
\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{equation}
\begin{gathered}
\eta_{c1} P_{pv}(k) + \eta_{c2} P_{bat}(k) \leq P_{conG,rate}
\\
P_{grid} + P_{load} \geq -P_{conG,rate}
\end{gathered}
\end{equation}
\begin{equation}
\begin{aligned}
\eta_{c1} P_{pv}(k) + \eta_{c2} P_{bat}(k) &\leq P_{conG,rate}
\\
P_{grid} + P_{load} &\geq -P_{conG,rate}
\end{aligned}
\end{equation}
\end{document}

Using the booktabs \midrule and with brackets

I am having trouble using \midrule in a latex longtable along with brackets. For example, here is my latex document (test.tex):
\documentclass[a4paper]{article}\usepackage[]{graphicx}\usepackage[]{color}
\usepackage{longtable}
\usepackage{booktabs}
\begin{document}
\begin{longtable}{|l|l|}
\caption{} \\
\toprule
test & estimate\\
\midrule
(Intercept) & 10.000 \\
test & 20.000 \\
\bottomrule
\end{longtable}
\end{document}
When running pdflatex on this file:
pdflatex test.tex
I run into these errors:
! Undefined control sequence.
<argument> ...al \expandafter \let \cmrsideswitch
\#tempa \fi \fi
l.12 (Intercept)
& 10.000 \\
Removing the brackets fixes the issue. And interestingly switching the order of the 2 rows works too [i.e. the (Intercept) row as the second row). I can't figure out what is wrong. Has anyone encountered this?
OK, so I had the same problem with code generated from Pandoc (with bracket after \toprule), I fixed it by using \toprule{} instead, it seems that toprule eats the bracket otherwise. Maybe this will help you.
Another possibilty is to put empty \hbox{} before the opening bracket, which I used, since I could not modify tex produced by pandoc (but pandoc is capable of parsing latex snippets in markdown).

How to write LaTeX in IPython Notebook?

How can I display LaTeX code in a IPython Notebook?
IPython notebook uses MathJax to render LaTeX inside html/markdown. Just put your LaTeX math inside $$.
$$c = \sqrt{a^2 + b^2}$$
Or you can display LaTeX / Math output from Python, as seen towards the end of the notebook tour:
from IPython.display import display, Math, Latex
display(Math(r'F(k) = \int_{-\infty}^{\infty} f(x) e^{2\pi i k} dx'))
This came up in a search I was just doing, found a better solution with some more searching, IPython notebooks now have a %%latex magic that makes the whole cell Latex without the $$ wrapper for each line.
Refer notebook tour for Rich Display System
LaTeX References:
Udacity's Blog has the Best LaTeX Primer I've seen: It clearly shows how to use LaTeX commands in easy to read, and easy to remember manner !! Highly recommended.
This Link has Excellent Examples showing both the code, and the rendered result !
You can use this site to quickly learn how to write LaTeX by example.
And, here is a quick Reference for LaTeX commands/symbols.
To Summarize: various ways to indicate LaTeX in Jupyter/IPython:
Examples for Markdown Cells:
inline, wrap in: $
The equation used depends on whether the the value of
$V​max​​$ is R, G, or B.
block, wrap in: $$
$$H← ​​​​​0 ​+​ \frac{​​30(G−B)​​}{Vmax−Vmin} ​​, if V​max​​ = R$$
block, wrap in: \begin{equation} and \end{equation}
\begin{equation}
H← ​​​60 ​+​ \frac{​​30(B−R)​​}{Vmax−Vmin} ​​, if V​max​​ = G
\end{equation}
block, wrap in: \begin{align} and \end{align}
\begin{align}
H←120 ​+​ \frac{​​30(R−G)​​}{Vmax−Vmin} ​​, if V​max​​ = B
\end{align}
Examples for Code Cells:
LaTex Cell: %%latex magic command turns the entire cell into a LaTeX Cell
%%latex
\begin{align}
\nabla \cdot \vec{\mathbf{E}} & = 4 \pi \rho \\
\nabla \times \vec{\mathbf{E}}\, +\, \frac1c\, \frac{\partial\vec{\mathbf{B}}}{\partial t} & = \vec{\mathbf{0}} \\
\nabla \cdot \vec{\mathbf{B}} & = 0
\end{align}
Math object to pass in a raw LaTeX string:
from IPython.display import Math
Math(r'F(k) = \int_{-\infty}^{\infty} f(x) e^{2\pi i k} dx')
Latex class. Note: you have to include the delimiters yourself. This allows you to use other LaTeX modes such as eqnarray:
from IPython.display import Latex
Latex(r"""\begin{eqnarray}
\nabla \times \vec{\mathbf{B}} -\, \frac1c\, \frac{\partial\vec{\mathbf{E}}}{\partial t} & = \frac{4\pi}{c}\vec{\mathbf{j}} \\
\nabla \cdot \vec{\mathbf{E}} & = 4 \pi \rho \\
\nabla \times \vec{\mathbf{E}}\, +\, \frac1c\, \frac{\partial\vec{\mathbf{B}}}{\partial t} & = \vec{\mathbf{0}} \\
\nabla \cdot \vec{\mathbf{B}} & = 0
\end{eqnarray}""")
Docs for Raw Cells:
(sorry, no example here, just the docs)
Raw cells
Raw cells provide a place in which you can write output directly. Raw cells are not evaluated by the notebook. When passed through nbconvert, raw cells arrive in the destination format unmodified. For example, this allows you to type full LaTeX into a raw cell, which will only be rendered by LaTeX after conversion by nbconvert.
Additional Documentation:
For Markdown Cells, as quoted from Jupyter Notebook docs:
Within Markdown cells, you can also include mathematics in a straightforward way, using standard LaTeX notation: $...$ for inline mathematics and $$...$$ for displayed mathematics. When the Markdown cell is executed, the LaTeX portions are automatically rendered in the HTML output as equations with high quality typography. This is made possible by MathJax, which supports a large subset of LaTeX functionality
Standard mathematics environments defined by LaTeX and AMS-LaTeX (the amsmath package) also work, such as \begin{equation}...\end{equation}, and \begin{align}...\end{align}. New LaTeX macros may be defined using standard methods, such as \newcommand, by placing them anywhere between math delimiters in a Markdown cell. These definitions are then available throughout the rest of the IPython session.
Use $$ if you want your math to appear in a single line, e.g.,
$$a = b + c$$ (line break after the equation)
If you don't need a line break after the math, use single dollar sign $, e.g.,
$a = b + c$ (no line break after the equation)
You can choose a cell to be markdown, then write latex code which gets interpreted by mathjax, as one of the responders say above.
Alternatively, Latex section of the iPython notebook tutorial explains this well.
You can either do:
from IPython.display import Latex
Latex(r"""\begin{eqnarray}
\nabla \times \vec{\mathbf{B}} -\, \frac1c\, \frac{\partial\vec{\mathbf{E}}}{\partial t} & = \frac{4\pi}{c}\vec{\mathbf{j}} \\
\nabla \cdot \vec{\mathbf{E}} & = 4 \pi \rho \\
\nabla \times \vec{\mathbf{E}}\, +\, \frac1c\, \frac{\partial\vec{\mathbf{B}}}{\partial t} & = \vec{\mathbf{0}} \\
\nabla \cdot \vec{\mathbf{B}} & = 0
\end{eqnarray}""")
or do this:
%%latex
\begin{align}
\nabla \times \vec{\mathbf{B}} -\, \frac1c\, \frac{\partial\vec{\mathbf{E}}}{\partial t} & = \frac{4\pi}{c}\vec{\mathbf{j}} \\
\nabla \cdot \vec{\mathbf{E}} & = 4 \pi \rho \\
\nabla \times \vec{\mathbf{E}}\, +\, \frac1c\, \frac{\partial\vec{\mathbf{B}}}{\partial t} & = \vec{\mathbf{0}} \\
\nabla \cdot \vec{\mathbf{B}} & = 0
\end{align}
More info found in this link
I developed prettyPy, which offers a nice way to print equation. Unfortunately, it's not performant and needs testing.
Example:
Granted, sympy is a great alternative and although prettyPy doesn't allow for evaluating expressions, variable initialization is not required.
I wrote how to write LaTeX in Jupyter Notebook in this article.
You need to enclose them in dollar($) signs.
To align to the left use a single dollar($) sign.
$P(A)=\frac{n(A)}{n(U)}$
To align to the center use double dollar($$) signs.
$$P(A)=\frac{n(A)}{n(U)}$$
Use \limits for \lim, \sum and \int to add limits to the top and the bottom of each sign.
Use a backslash to escape LaTeX special words such as Math symbols, Latin words, text, etc.
Try this one.
$$\overline{x}=\frac{\sum \limits _{i=1} ^k f_i x_i}{n} \text{, where } n=\sum \limits _{i=1} ^k f_i $$
Matrices
Piecewise functions
$$
\begin{align}
\text{Probability density function:}\\
\begin{cases}
\frac{1}{b-a}&\text{for $x\in[a,b]$}\\
0&\text{otherwise}\\
\end{cases}
\\
\text{Cumulative distribution function:}\\
\begin{cases}
0&\text{for $x<a$}\\
\frac{x-a}{b-a}&\text{for $x\in[a,b)$}\\
1&\text{for $x\ge b$}\\
\end{cases}
\end{align}
$$
The above code will create this.
If you want to know how to add numbering to equations and align equations, please read this article for details.
Since, I was not able to use all the latex commands in Code even after using the %%latex keyword or the $..$ limiter, I installed the nbextensions through which I could use the latex commands in Markdown. After following the instructions here: https://github.com/ipython-contrib/IPython-notebook-extensions/blob/master/README.md and then restarting the Jupyter and then localhost:8888/nbextensions and then activating "Latex Environment for Jupyter", I could run many Latex commands. Examples are here: https://rawgit.com/jfbercher/latex_envs/master/doc/latex_env_doc.html
\section{First section}
\textbf{Hello}
$
\begin{equation}
c = \sqrt{a^2 + b^2}
\end{equation}
$
\begin{itemize}
\item First item
\item Second item
\end{itemize}
\textbf{World}
As you see, I am still unable to use usepackage. But maybe it will be improved in the future.
The answer given by minrk (included for completeness) is good, but there is another way that I like even more.
You can also render an entire cell as LaTeX by typing %%latex as the first line in a text cell. This is usefull if you
want more control,
want more than just a math environment,
or if you are going to write a lot of math in one cell.
minrk's answer:
IPython notebook uses MathJax to render
LaTeX inside html/markdown. Just put your LaTeX math inside $$.
$$c = \sqrt{a^2 + b^2}$$
Or you can display LaTeX / Math output from Python, as seen towards
the end of the notebook
tour:
from IPython.display import display, Math, Latex
display(Math(r'F(k) = \int_{-\infty}^{\infty} f(x) e^{2\pi i k} dx'))
If your main objective is doing math, SymPy provides an excellent approach to functional latex expressions that look great.
Using LaTeX syntax directly in a Markdown cell works for me. I'm using Jypiter 4.4.0.
I don't have to use %%latex magic command, I insist, simply a markdown cell:
\begin{align}
\nabla \times \vec{\mathbf{B}} -\, \frac1c\, \frac{\partial\vec{\mathbf{E}}}{\partial t} & = \frac{4\pi}{c}\vec{\mathbf{j}} \\
\nabla \cdot \vec{\mathbf{E}} & = 4 \pi \rho \\
\nabla \times \vec{\mathbf{E}}\, +\, \frac1c\, \frac{\partial\vec{\mathbf{B}}}{\partial t} & = \vec{\mathbf{0}} \\
\nabla \cdot \vec{\mathbf{B}} & = 0
\end{align}
Renders to:
I came across this problem some day using colab. And I find the most painless way is just running this code before printing. Everything works like charm then.
from IPython.display import Math, HTML
def load_mathjax_in_cell_output():
display(HTML("<script src='https://www.gstatic.com/external_hosted/"
"mathjax/latest/MathJax.js?config=default'></script>"))
get_ipython().events.register('pre_run_cell', load_mathjax_in_cell_output)
import sympy as sp
sp.init_printing()
The result looks like this:
I am using Jupyter Notebooks.
I had to write
%%latex
$sin(x)/x$
to get a LaTex font.
Yet another solution for when you want to have control over the document preamble. Write a whole document, send it to system latex, convert the pdf to png, use IPython.display to load and display.
import tempfile
import os.path
import subprocess
from IPython.display import Image, display
with tempfile.TemporaryDirectory(prefix="texinpy_") as tmpdir:
path = os.path.join(tmpdir, "document.tex")
with open(path, 'w') as fp:
fp.write(r"""
\documentclass[12pt]{standalone}
\begin{document}
\LaTeX{}
\end{document}
""")
subprocess.run(["lualatex", path], cwd=tmpdir)
subprocess.run(["pdftocairo", "-singlefile", "-transp", "-r", "100", "-png", "document.pdf", "document"], cwd=tmpdir)
im = Image(filename=os.path.join(tmpdir, "document.png"))
display(im)
If you want to display a LaTeX equation from a notebook code cell you can create a simple wrapper class that makes use of the Jupyter notebooks rich display representation. This class should have a _repr_latex_ method (note this single underscore at the start and end rather than the double underscores of other special methods) that outputs the LaTeX string. E.g.:
class LaTeXEquation:
def __init__(self, eqntext):
self.eqntext = eqntext
def __repr__(self):
return repr(self.eqntext)
def _repr_latex_(self):
"""
Special method for rich display of LaTeX formula.
"""
# add $'s at start and end if not present
if self.eqntext.strip()[0] != "$" and self.eqntext.strip()[-1] != "$":
return "$" + self.eqntext + "$"
else:
return self.eqntext
myeqn = "x = y^2"
Then in a code cell, if you do, e.g.,
LaTeXEquation(myeqn)
it will show the formatted equation.

Error while writing multi-valued function in LateX

I am creating a document in LateX and the following multivalued function has been giving me trouble for a while.
The Latex code for the above as I gave is
$\[delta \tau_{i,j}^{k}$ = $\left\{$
\begin{array}{l l}
\frac{1}{L_{k}} & \quad \mbox{if ant k travels on edge \textit{i,j}} \\
0 & \quad \mbox{otherwise}
\end{array} \right. \]
While compiling it gives me the following error
! LaTeX Error: Bad math environment delimiter.
See the LaTeX manual or LaTeX Companion for explanation.
Type H <return> for immediate help.
...
l.52 $\[
delta \tau_{i,j}^{k}$ = $\left\{$
?
Any help on fixing this error would be much appreciated.
aschepler is right--it's the [ inside the $.
You may also want to consider the cases environment, which I think is easier for this sort of thing. For you example, you'd have:
\[
\Delta\tau_{i,j}^k=
\begin{cases}
1/L_k & \text{if ant $k$ travels along edge $i,j$} \\
0 & \text{otherwise}
\end{cases}
\]
You can't use both $ $ and \[ \] like that. $ is for in-line equations (fit within a paragraph of text), so you should probably use just \[ \] around your equation and remove all the $s.

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