Cfrgtkky

I want to use siunitx package for writing the units in my document. However, just adding the line:

usepackage{siunitx}

to the document (and without even using the siunitx commands) gives 84 errors of the type: Missing '}'... Missing '$' ... Extra '}' ... and so on.

Without this line the document compiles and generated fine.

I have managed to locate the source causing the problem, which is the use of math code inside a tabularx.

Here is minimal code to compile:

documentclass[12pt,twoside]{report}

usepackage{siunitx}

usepackage{comment}

usepackage{tabularx}

newcolumntype{Y}{>{centeringarraybackslash}X}

newcolumntype{s}{>{hsize=.25hsizecenteringarraybackslash}X}



begin{document}

begin{center} 

begin {table}[h]

caption{Comparison between bla bla bla}

centering

{

    renewcommand{arraystretch}{1.5} % renewcommand{arraystretch}{1.5}

    begin{tabularx}{0.95linewidth} {Y|s}   

    hlinehline

    column 1 title & column 2 title tabularnewline % [0.5cm]  

    hline%hline

    cell(1,1) & $textrm{w}_0$ tabularnewline

%begin{comment}

    cell(2,1) & $frac{textrm{w}_0}{sqrt{2}}approx 0.7textrm{w}_0$ tabularnewline

    cell(3,1) & $frac{textrm{w}_0}{sqrt{3}}approx 0.58textrm{w}_0$ tabularnewline

    cell(4,1) & $0.5textrm{w}_0$ tabularnewline

    cell(5,1) & $0.46textrm{w}_0$ tabularnewline



    hline

%end{comment}

    end{tabularx}

}

label{tab:comparing_table}

end{table} 

%

end{center} 

end{document}

Now, without the: usepackage{siunitx} the above table compiles just fine.
The problem is with the math code inside the table. The same table with text only also compiles fine.

How can I keep the table with the math in it and with siunitx ???

It seems to me that the problem comes from your custom columntype since using j instead of s works flawless for me.
The s is reserved by the siunitx package.

documentclass[12pt,twoside]{report}

usepackage{siunitx}

usepackage{comment}

usepackage{tabularx}

newcolumntype{Y}{>{centeringarraybackslash}X}

newcolumntype{j}{>{hsize=.25hsizecenteringarraybackslash}X}



begin{document}

begin{center} 

begin{table}[h]

caption{Comparison between bla bla bla}

centering

{

    renewcommand{arraystretch}{1.5} % 

    begin{tabularx}{0.95linewidth}{Y|j}   

    hlinehline

    column 1 title & column 2 title tabularnewline % [0.5cm]  

    hline%hline

    cell(1,1) & {$textrm{w}_0$}  tabularnewline

    cell(2,1) & $frac{textrm{w}_0}{sqrt{2}}approx 0.7textrm{w}_0$ tabularnewline

    cell(3,1) & $frac{textrm{w}_0}{sqrt{3}}approx 0.58textrm{w}_0$ tabularnewline

    cell(4,1) & $0.5textrm{w}_0$ tabularnewline

    cell(5,1) & $0.46textrm{w}_0$ tabularnewline

    hline

end{tabularx}

}

label{tab:comparing_table}

end{table} 

end{center} 

end{document}

The console output (and the log file) shows

Package array Warning: Column s is already defined on input line 8.

When a column type is already defined, array usually warns and overwrites the definition. But Catch 22 is there waiting for us! The s column type is defined by siunitx, so the warning is shown, but siunitx actually does the necessary definition for the column type at begin document! So you end up anyway with the s column type defined by siunitx and this causes the error, because the input in that column is invalid.

If you aren't sure that overwriting a column type is safe, don't do it.

There are a few other points to note.

1. Never place table inside center: this has the only effect of producing unwanted vertical space in the document and the table may or may not be in the middle of that vertical space.




2. Avoid begin{table}[h] in the hope the float will actually be placed here. It usually won't. LaTeX converts [h] to [ht], but big floats might not find their place in the specified positions and you end up delaying it and all subsequent floats until the end of the current chapter.




3. Using a group to localize the effect of renewcommand{arraystretch}{1.5} is useless, because the former value will be restored anyway after end{table}.




4. Put your label next to the caption, which it belongs to.



5. 
   

   The correct way to go for using “variable X columns” is to use hsize=<frac>hsize so that the sum of all fractions is the total number of X columns. In your case if the subdivision is 3/4 for the first column and 1/4 for the second column it should be

   
   
   

   >{hsize=1.5hsize}X >{hsize=0.5hsize}X
   
   

   
   

Full code, with booktabs features rather than hlinehline and vertical rules.

documentclass[12pt,twoside]{report}

usepackage{siunitx}

usepackage{comment}

usepackage{tabularx}

usepackage{booktabs}



begin{document}



begin{table}[htp]

caption{Comparison between bla bla bla}

label{tab:comparing_table}



centering

renewcommand{arraystretch}{1.5}



begin{tabularx}{0.95linewidth}

 {

  >{centeringhsize=1.5hsize}X

  >{centeringhsize=0.5hsize}X

 }

toprule

column 1 title & column 2 title tabularnewline % [0.5cm]  

midrule

    cell(1,1) & $textrm{w}_0$ tabularnewline

%begin{comment}

    cell(2,1) & $frac{textrm{w}_0}{sqrt{2}}approx 0.7textrm{w}_0$ tabularnewline

    cell(3,1) & $frac{textrm{w}_0}{sqrt{3}}approx 0.58textrm{w}_0$ tabularnewline

    cell(4,1) & $0.5textrm{w}_0$ tabularnewline

    cell(5,1) & $0.46textrm{w}_0$ tabularnewline



bottomrule

%end{comment}

end{tabularx}



end{table} 



end{document}

Here is the output with

>{centering}X c

for the column specifications: