line delimiter for file export

Hi,

I am trying to export a matrix to a file. Collumns shall be delimited by comma, lines shall be delimited by 'space'. The exported file shall only have one row.

e.g. matrix=[a b c,d e f,g h i]

export.txt a,b,c d,e,f g,h,i

I have tried several functions but I can't set the line delimiter to 'space'. (dlmwrite, save, csvwrite)