SpecializedCsv.ps1

# In reply to https://www.reddit.com/r/PowerShell/comments/46bwtd/help_with_counting_in_csv_files/

# Tested against test csvs generated by the other script in this gist, and it worked without modification!

param (
    $Path = ".",
    $OutFile = "C:\temp\countlines.csv"
)

Get-ChildItem -Filter *.csv -Path $Path -Recurse |
    ForEach-Object {
        $File = $_

        # Blank the Sums hash
        $Sums = @{}

        # Count each Hour value by using it as the hash key and adding to the value
        # New to me: +=1 to a nonexistent key makes that key value 1 ... how convenient!
        Import-Csv -Path $File.FullName |
            ForEach-Object {
                $Sums[($_.Hour)] += 1
            }

        $Sums.Keys | ForEach-Object {
            $Hour = $_
            $Count = $Sums[$_]
            New-Object psobject -Property ([ordered]@{
                Name = $File.name
                Hour = $Hour
                Count = $Count
                SecretSauce = ($Count * $Hour * 60) / (20106.19298 * $Hour * 60) * ([math]::Exp($Hour/123))
            })
        }
    } |
    Export-Csv -NoTypeInformation -Path $OutFile

z-GenTestCsvs.ps1

$NumCsvs = 5
$NumRows = 100

$Hours = -120..0

1..$NumCsvs | ForEach-Object {
    1..$NumRows | ForEach-Object {
        New-Object psobject -Property @{ Hour = Get-Random $Hours }
    } |
        Export-Csv -NoTypeInformation -Path "$_.csv"
}