Gdddk

I have the following Latex table I generated with the KableExtra package in R. What I want to do now is make all columns the same/fixed width and align on decimals. The second of these is not to be supported by KableExtra so I will need to do this in Latex directly. The siunitx package seems a good choice for this, but I can't get it to work.

documentclass[12pt,a4paper]article
usepackagegeometry
usepackageamsmath
usepackagebooktabs
usepackagefloat
usepackagesiunitx
begindocument

begintable[H]
 centering
 begintabularccccccccc
 toprule
 multicolumn1c & multicolumn4cCumulative change & multicolumn4cMarginal change \
 cmidrule(lr)2-5 cmidrule(lr)6-9
 $k$ & $(Cons.)$ & $Spread_t$ & $overlineR^2$ & $SEE$ & $(Cons.)$ & $Spread_t$ & $overlineR^2$ & $SEE$\
 midrule
 $1$ & $1.76^**$ & $2.09^**$ & $0.18$ & $4.05$ & $1.76^**$ & $2.09^**$ & $0.18$ & $4.05$\
 & $(0.56)$ & $(0.40)$ & & & $(0.56)$ & $(0.40)$ & & \
 $2$ & $1.73^**$ & $2.06^**$ & $0.28$ & $3.02$ & $1.78^**$ & $2.06^**$ & $0.17$ & $4.06$\
 & $(0.39)$ & $(0.29)$ & & & $(0.52)$ & $(0.39)$ & & \
 $8$ & $2.65^**$ & $0.96^**$ & $0.18$ & $1.70$ & $ 4.21^**$ & $-0.59 $ & $0.00$ & $4.45$\
 & $(0.26)$ & $(0.16)$ & & & $(0.64)$ & $(0.53)$ & & \
 $12$ & $3.31^**$ & $0.35^*$ & $0.04$ & $1.39$ & $ 4.52^**$ & $-0.93^**$ & $0.07$ & $2.66$\
 & $(0.19)$ & $(0.14)$ & & & $(0.32)$ & $(0.30)$ & & \
 bottomrule
 multicolumn9ltextitNote: \
 multicolumn9lRobust standard errors in parentheses.\
 multicolumn9l$^*$ $p < 0.05$, $^**$ $p < 0.01$ in a two-tailed test.\
 endtabular
endtable

enddocument

The fixed column width I tried to achieve with *9S[table-column-width = 2 cm], but this gave me a lot of "! Extra , or forgotten $." type errors.

For the alignment I tried to make something out of this and other answers and the siunutx manual, but I got a whole bunch of errors and problems where my significance stars disappeared, etc. I want to center all columns, but aligned on the decimal. The first columns should be aligned on the implicit decimal.

Thanks!

with use of S column type from package siunitx:

(red lines indicate text borders)

i would also use threepartablex package for simpler writing table notes (...tnote** instead of $...^**$). it also provide command note for tablenotes environment:

documentclass[12pt,a4paper]article
usepackagegeometry
usepackageamsmath
usepackagebooktabs
usepackage[referable]threeparttablex % <--- for note, source
usepackagesiunitx

begindocument

begintable[htb]
 centering
beginthreeparttable
 captionTable title
 labeltab:statistic
begintabular*linewidth@hskiptabcolsepextracolsepfill
 c *8S[table-format=1.2,
 input-symbols=( ),
 table-space-text-post=**
 ]
 toprule
multicolumn1c 
 & multicolumn4cCumulative change
 & multicolumn4cMarginal change \
 cmidrule(lr)2-5 cmidrule(lr)6-9
$k$ & (Cons.) & Spread$_t$ & $overlineR^2$& SEE
 & (Cons.) & Spread$_t$ & $overlineR^2$& SEE \
 midrule
1 & 1.76tnote** & 2.09tnote** & 0.18 & 4.05
 & 1.76tnote** & 2.09tnote** & 0.18 & 4.05 \
 & (0.56) & (0.40) & &
 & (0.56) & (0.40) & & \
2 & 1.73tnote** & 2.06tnote** & 0.28 & 3.02
 & 1.78tnote** & 2.06tnote** & 0.17 & 4.06 \
 & (0.39) & (0.29) & &
 & (0.52) & (0.39) & & \
 bottomrule
endtabular*
 begintablenotes[para, flushleft]footnotesize
 note: Robust standard errors in parentheses.\
 item[*] $p < 0.05$,
 item[**] $p < 0.01$ in a two-tailed test.
 endtablenotes
endthreeparttable
endtable

enddocument

edit:
i miss requirement that all column should have equal width. this can be achieved for example with use of tabularx table environment where for column headers is used command mcx defined in preamble as:

newcommandmcx[2]multicolumn1>centeringarraybackslashX#1

to my taste this requirement not result in a better looking table:

documentclass[12pt,a4paper]article
usepackagegeometry
usepackageamsmath
usepackagebooktabs, tabularx
newcommandmcx[1]multicolumn1>centeringarraybackslashX#1
usepackage[referable]threeparttablex 
usepackagesiunitx

begindocument

begintable[htb]
 centering
 sisetuptable-format=1.2, input-symbols=( )
beginthreeparttable
 captionTable title
 labeltab:statistic
begintabularxlinewidth@hskiptabcolsepextracolsepfill
 >centeringarraybackslashX 
 *2S[table-space-text-post=**]
 *2S
 *2S[table-space-text-post=**]
 *2S
 
 toprule
multicolumn1c 
 & multicolumn4cCumulative change
 & multicolumn4cMarginal change \
 cmidrule(lr)2-5 cmidrule(lr)6-9
$k$ & mcx(Cons.) & mcxSpread$_t$ 
 & mcx$overlineR^2$ & SEE
 & mcx(Cons.) & mcxSpread$_t$ 
 & mcx$overlineR^2$ & mcxSEE \
 midrule
1 & 1.76tnote** & 2.09tnote** & 0.18 & 4.05
 & 1.76tnote** & 2.09tnote** & 0.18 & 4.05 \
 & (0.56) & (0.40) & &
 & (0.56) & (0.40) & & \
2 & 1.73tnote** & 2.06tnote** & 0.28 & 3.02
 & 1.78tnote** & 2.06tnote** & 0.17 & 4.06 \
 & (0.39) & (0.29) & &
 & (0.52) & (0.39) & & \
 bottomrule
endtabularx
 begintablenotes[para, flushleft]footnotesize
 note Robust standard errors in parentheses.\
 item[*] $p < 0.05$,
 item[**] $p < 0.01$ in a two-tailed test.
 endtablenotes
endthreeparttable
endtable

enddocument