Exporting dataset with NumberForm

Question

I have a dataset which includes strings and numbers. I want to export it in CSV with all numbers being printed with 2 decimals. I tried several functions like

mydataset=NumberForm[#, {Infinity, 2}] & /@ mydataset

or using $PrePrint command but did not succeed to do what I want. Thanks for your help.

Answer 1

This should work

dataset[All, All, NumberForm[#, {Infinity, 2}] &] 
%[Values[#] & // Normal]
Export["test.csv", %]

which when applied to the following example

dataset = Dataset[{
   <|"a" -> 1, "b" -> "xman", "c" -> 1|>,
   <|"a" -> 2, "b" -> "bear", "c" -> N[Pi]|>,
   <|"a" -> 3, "b" -> "fear", "c" -> 3|>,
   <|"a" -> 4, "b" -> "smear", "c" -> 5|>,
   <|"a" -> 5, "b" -> "year", "c" -> 7|>,
   <|"a" -> 6, "b" -> "ear", "c" -> 12.4335|>}]

gives

\begin{array}{ccc} 1.00,xman,1.00\\ 2.00,bear,3.14\\ 3.00,fear,3.00\\ 4.00,smear,5.00\\ 5.00,year,7.00\\ 6.00,ear,12.43\\ \end{array}

in the exported file

Update 1

The code update that does not strip the string from quotation marks

ClearAll[tonum]
tonum[x_?NumericQ] := NumberForm[x, {Infinity, 2}]
tonum[x_] := x
Export["test.csv", 
 Map[tonum, ds[Values] // Normal, {2}]]

and the output is

gives

\begin{array}{ccc} 1.00,"xman",1.00\\ 2.00,"bear",3.14\\ 3.00,"fear",3.00\\ 4.00,"smear",5.00\\ 5.00,"year",7.00\\ 6.00,"ear",12.43\\ \end{array}

Update 2

It appears that the Export strips double quotes when the string is Wrapped with NumberForm. Number form has no effect when displaying string the in front end. I do not know if this is intended behavior of export or a bug.

Answer 2

Really sorry for my english, I was speaking about the question marks of strings, not the parenthesis. Based on your help, this works :

Export["output.CSV",ds[All,All,If[NumberQ[#]==True,NumberForm[#,{Infinity,2}],#]&][Values[#]&//Normal]]