---

For a full list of BASHing data blog posts see the index page.     

---

How to stack columns

---

A simple case. Here's "fileA", a tab-separated table (TSV) with some missing values:

aaa	ggg	mmm	sss	yyy
bbb	hhh	nnn	ttt	zzz
ccc	iii	ooo	uuu
ddd	jjj		vvv
	kkk	qqq	www
fff	lll	rrr	xxx

The easiest way I know to stack up the columns (column 1 on top of column 2 on top of column 3, etc) is to first get the number of columns from the first line (I use AWK for that job), then print the results of progressively cutting out each column:

cols=$(awk -F"\t" 'NR==1 {print NF}' fileA)
 
for ((i=1;i<="$cols";i++)); do cut -f"$i" fileA; done

---

Not so simple. Stacking gets a little trickier when adjoining columns need to be stacked together. For example, here's "fileB", again tab-separated, with each group of letters having a corresponding number:

aaa	001	ggg	007	mmm	013	sss	019	yyy	025
bbb	002	hhh	008	nnn	014	ttt	020	zzz	026
ccc	003	iii	009	ooo	015	uuu	021
ddd	004	jjj	010			vvv	022
		kkk	011	qqq	017	www	023
fff	006	lll	012	rrr	018	xxx	024

A simple approach is to loop through the odd-numbered columns, cutting and stacking the odd-numbered columns together with the next even-numbered ones:

cols=$(awk -F"\t" 'NR==1 {print NF}' fileB)
 
for ((i=1;i<="$cols";i+=2)); \
do cut -f"$i","$(($i+1))" fileB; done

---

Last update: 2020-11-25
The blog posts on this website are licensed under a
Creative Commons Attribution-NonCommercial 4.0 International License

---