Converting CSV Column to Rows - powershell

Question

I'm trying to create a PowerShell script that transpose a CSV file from column to rows.
I found examples of doing the opposite (converting row based CSV to column) but I found nothing on column to rows. My problem being that I don't know exactly how many column I'll have. I tried adapting the row to column to column to rows but unsuccessfully.
$a = Import-Csv "input.csv"
$a | FT -AutoSize
$b = #()
foreach ($Property in $a.Property | Select -Unique) {
$Props = [ordered]#{ Property = $Property }
foreach ($Server in $a.Server | Select -Unique){
$Value = ($a.where({ $_.Server -eq $Server -and
$_.Property -eq $Property })).Value
$Props += #{ $Server = $Value }
}
$b += New-Object -TypeName PSObject -Property $Props
}
$b | FT -AutoSize
$b | Out-GridView
$b | Export-Csv "output.csv" -NoTypeInformation
For example my CSV can look like this:
"ID","DATA1"
"12345","11111"
"54321","11111"
"23456","44444"
or this (number of column can vary):
"ID","DATA1","DATA2","DATA3"
"12345","11111","22222","33333"
"54321","11111",,
"23456","44444","55555",
and I would like the script to convert it like this:
"ID","DATA"
"12345","11111"
"12345","22222"
"12345","33333"
"54321","11111"
"23456","44444"
"23456","55555"

Answer 1

The trick is to query the members of the table to get the column names. Once you do that then the rest is straightforward:
function Flip-Table ($Table) {
Process {
$Row = $_
# Get all the columns names, excluding the ID field.
$Columns = ($Row | Get-Member -Type NoteProperty | Where-Object Name -ne ID).Name
foreach ($Column in $Columns) {
if ($Row.$Column) {
$Properties = [Ordered] #{
"ID" = $Row.ID
"DATA" = $Row.$Column
}
New-Object PSObject -Property $Properties
}
}
# Garbage collection won't kick in until the end of the script, so
# invoke it every 100 input rows.
$Count++;
if (($Count % 100) -eq 0) {
[System.GC]::GetTotalMemory('forceFullCollection') | out-null
}
}
}
Import-Csv input.csv | Flip-Table | Export-Csv -NoTypeInformation output.csv

Answer 2

Well, here is mine. I'm not as fancy as the rest:
$in = Get-Content input.csv | Select -Skip 1
$out = New-Object System.Collections.ArrayList
foreach($row in $in){
$parts = $row.Split(',')
$id = $parts[0]
foreach($data in $parts[1..$parts.Count]){
if($data -ne '' -AND $data -ne $null){
$temp = New-Object PSCustomObject -Property #{'ID' = $id;
'Data' = $data}
$out.Add($temp) | Out-Null
}
}
}
$out | Export-CSV output.csv -NoTypeInformation

Answer 3

You can do something like this
# Convert csv to object
$csv = ConvertFrom-Csv #"
"ID","DATA1","DATA2","DATA3"
"12345","11111","22222","33333"
"54321","11111",,
"23456","44444","55555"
"#
# Ignore common members and the ID property
$excludedMembers = #(
'GetHashCode',
'GetType',
'ToString',
'Equals',
'ID'
)
$results = #()
# Iterate around each csv row
foreach ($row in $csv) {
$members = $row | Get-Member
# Iterate around each member from the 'row object' apart from our
# exclusions and empty values
foreach ($member in $members |
Where { $excludedMembers -notcontains $_.Name -and $row.($_.Name)}) {
# add to array of objects
$results += #{ ID=$row.ID; DATA=$row.($member.Name)}
}
}
# Write the csv string
$outstring = "ID,DATA"
$results | foreach { $outstring += "`n$($_.ID),$($_.DATA)" }
# New csv object
$csv = $outstring | ConvertFrom-Csv
Probably not the most elegant solution, but should do what you need
I left some comments explaining what it does

Answer 4

If you only want to accept a limited number DATA columns (e.g. 5), you could do:
ForEach ($i in 1..5) {$CSV | ? {$_."Data$i"} | Select ID, #{N='Data'; E={$_."Data$i"}}}
And if you have a potential unlimited number of DATA columns:
ForEach ($Data in ($CSV | Select "Data*" -First 1).PSObject.Properties.Name) {
$CSV | ? {$_.$Data} | Select ID, #{N='Data'; E={$_.$Data}}
}