Rearranging a csv file - bash

Question

I have a file with contents similar to the below
Boy,Football
Boy,Football
Boy,Football
Boy,Squash
Boy,Tennis
Boy,Football
Girl,Tennis
Girl,Squash
Girl,Tennis
Girl,Tennis
Boy,Football
How can I use 'awk' or similar to rearrange this to the below:
Football Tennis Squash
Boy 5 1 1
Girl 0 3 1
I'm not even sure if this is possible, but any help would be great.

Answer 1

$ cat tst.awk
BEGIN{ FS=","; OFS="\t" }
{
genders[$1]
sports[$2]
count[$1,$2]++
}
END {
printf ""
for (sport in sports) {
printf "%s%s", OFS, sport
}
print ""
for (gender in genders) {
printf "%s", gender
for (sport in sports) {
printf "%s%s", OFS, count[gender,sport]+0
}
print ""
}
}
$ awk -f tst.awk file
Squash Tennis Football
Boy 1 1 5
Girl 1 3 0
In general when you know the end point of the loop you put the OFS or ORS after each field:
for (i=1; i<=n; i++) {
printf "%s%s", $i, (i<n?OFS:ORS)
}
but if you don't then you put the OFS before the second and subsequent fields and print the ORS after the loop:
for (x in array) {
printf "%s%s", (++i>1?OFS:""), array[x]
}
print ""
I do like the:
n = length(array)
for (x in array) {
printf "%s%s", array[x], (++i<n?OFS:ORS)
}
idea to get the end of the loop too, but length(array) is gawk-specific.
Another approach to consider:
$ cat tst.awk
BEGIN{ FS=","; OFS="\t" }
{
for (i=1; i<=NF; i++) {
if (!seen[i,$i]++) {
map[i,++num[i]] = $i
}
}
count[$1,$2]++
}
END {
for (i=0; i<=num[2]; i++) {
printf "%s%s", map[2,i], (i<num[2]?OFS:ORS)
}
for (i=1; i<=num[1]; i++) {
printf "%s%s", map[1,i], OFS
for (j=1; j<=num[2]; j++) {
printf "%s%s", count[map[1,i],map[2,j]]+0, (j<num[2]?OFS:ORS)
}
}
}
$ awk -f tst.awk file
Football Squash Tennis
Boy 5 1 1
Girl 0 1 3
That last will print the rows and columns in the order they were read. Not quite as obvious how it works though :-).

Answer 2

I would just loop normally:
awk -F, -v OFS="\t" '
{names[$1]; sport[$2]; count[$1,$2]++}
END{printf "%s", OFS;
for (i in sport)
printf "%s%s", i, OFS;
print "";
for (n in names) {
printf "%s%s", n, OFS
for (s in sport)
printf "%s%s", count[n,s]?count[n,s]:0, OFS; print ""
}
}' file
This keeps track of three arrays: names[] for the first column, sport[] for the second column and count[name,sport] to count the occurrences of every combination.
Then, it is a matter of looping through the results and printing them in a fancy way and making sure 0 is printed if the count[a,b] does not exist.
Test
$ awk -F, -v OFS="\t" '{names[$1]; sport[$2]; count[$1,$2]++} END{printf "%s", OFS; for (i in sport) printf "%s%s", i, OFS; print ""; for (n in names) {printf "%s%s", n, OFS; for (s in sport) printf "%s%s", count[n,s]?count[n,s]:0, OFS; print ""}}' a
Squash Tennis Football
Boy 1 1 5
Girl 1 3 0
Format is a bit ugly, there are some trailing OFS.
To get rid of trailing OFS:
awk -F, -v OFS="\t" '{names[$1]; sport[$2]; count[$1,$2]++} END{printf "%s", OFS; for (i in sport) {cn++; printf "%s%s", i, (cn<length(sport)?OFS:ORS)} for (n in names) {cs=0; printf "%s%s", n, OFS; for (s in sport) {cs++; printf "%s%s", count[n,s]?count[n,s]:0, (cs<length(sport)?OFS:ORS)}}}' a
You can always pipe to column -t for a nice output.