How to start a new column after every nth row?

[shubk]

Hi have a file(comma separated) with 3 columns. I want to start new column after every 4th row
Input:
col1,col2,col3
1,disease1,high
1,disease2,low
1,disease3,high
col1,col2,col3
2,disease1,low
2,disease2,low
2,disease3,high

Expected output:
col1,col2,col3,col1,col2,col3
1,disease1,high,2,disease1,low
1,disease2,low,2,disease2,low
1,disease3,high,2,disease3,high

[finswimmer]

This should be possible with some unix commands and datamash.

cat input.txt|paste - - - -|datamash transpose --output-delimiter , > output.txt

This will for lines into one line. Than we use datamash to transpose this new table.

fin swimmer