Sort an associative array in awk - sorting

Question

I have an associative array in awk that gets populated like this:
chr_count[$3]++
When I try to print my chr_counts, I use this:
for (i in chr_count) {
print i,":",chr_count[i];
}
But not surprisingly, the order of i is not sorted in any way.
Is there an easy way to iterate over the sorted keys of chr_count?

Answer 1

Instead of asort, use asorti(source, destination) which sorts the indices into a new array and you won't have to copy the array.
Then you can use the destination array as pointers into the source array.
For your example, you would use it like this:
n=asorti(chr_count, sorted)
for (i=1; i<=n; i++) {
print sorted[i] " : " chr_count[sorted[i]]
}

Answer 2

you can use the sort command. e.g.
for ( i in data )
print i ":", data[i] | "sort"

Answer 3

I recently came across this issue and found that with gawk I could set the value of PROCINFO["sorted_in"] to control iteration order. I found a list of valid values for this by searching for PROCINFO online and landed on this GNU Awk User's Guide page: https://www.gnu.org/software/gawk/manual/html_node/Controlling-Scanning.html
This lists options of the form #{ind|val}_{num|type|str}_{asc|desc} with:
ind sorting by key (index) and val sorting by value.
num sorting numerically, str by string and type by assigned type.
asc for ascending order and desc for descending order.
I simply used:
PROCINFO["sorted_in"] = "#val_num_desc"
for (i in map) print i, map[i]
And the output was sorted in descending order of values.

Answer 4

Note that asort() and asorti() are specific to gawk, and are unknown to awk. For plain awk, you can roll your own sort() or get one from elsewhere.

Answer 5

This is taken directly from the documentation:
populate the array data
# copy indices
j = 1
for (i in data) {
ind[j] = i # index value becomes element value
j++
}
n = asort(ind) # index values are now sorted
for (i = 1; i <= n; i++) {
do something with ind[i] Work with sorted indices directly
...
do something with data[ind[i]] Access original array via sorted indices
}