How to aggregate multiple rows into one in CSV? - parsing

Question

I have following problem:
I have a CSV file, which looks like this:
1,12
1,15
1,18
2,10
2,11
3,20
And I would like to parse it somehow to get this:
1,12,15,18
2,10,11
3,20
Do you have any solution? Thanks!

Answer 1

Here is one solution for you.
This first part just sets up the example for testing. I am assuming you already have a file with values in the second part of the script.
$path = "$env:TEMP\csv.txt"
$data =#"
1,12
1,15
1,18
2,10
2,11
3,20
"#
$data | Set-Content $path
This should be all you need:
$path = "$env:TEMP\csv.txt"
$results = #{}
foreach($line in (Get-Content $path))
{
$split = $line -split ','
$rowid = $split[0]
$data = $split[1]
if(-not($results.$rowid))
{
$results.$rowid = $rowid
}
$results.$rowid += "," + $data
}
$results.values | Sort-Object
Your original dataset does not need to be sorted for this one to work. I slice the data up and insert it into a hashtable.

Answer 2

I don't know your exact code requirement. I will try to write some logic which may help you!
CSV means a text file which I can read into a string or an array
If one will look at the above CSV data, there is a common pattern i.e. after each pair there is a space in-between.
So my parsing will be depending on 2 phases
parse with ' ' i.e. single space and will insert into an array (say elements)
then parse with ',' i.e. comma from each element of elements and save into another array (say details) where odd indexes will be containing the left hand values and even indexes will be containing the right hand values.
So next while printing or using skip the odd index if you have an existing value.
Hope this helps...

Answer 3

Satyaranjan,
thanks for your answer! To clarify - I don't have any code requirements, I can use any language to achieve results. The point is to take unique values from first position (1,2,3) and put all related numbers on the right (1 - 12, 15 and 18 etc.). It is something like GROUP_CONCAT function in MySQL - but unfortunately I don't have such a function, so I am looking for some workaround.
Hope it is more clear now. Thanks