Generate simple histogram in PowerShell. Displays frequency that an item occurs in a list.

Histogram.ps1

function Histogram {
        [CmdletBinding()]
        [Alias("hgram")]
        param (
            [Parameter(ValueFromPipeline=$True,ValueFromPipelineByPropertyName=$True)]
            [object[]]$Items,
            [Parameter(Position=1)]
            [string]$Property,
            [ValidateRange(2,[int]::MaxValue)]
            [int]$Scale = 40,
            [char]$Visual = '*',
            [ref]$breakdown_ref,
            [switch]$ShowStats,
            [switch]$Numerical,
            [switch]$Sort,
            [switch]$Descending,
            [switch]$PassThru,
            [ValidateRange(2,20)]
            [int]$BucketsCount=10
            )
    begin {
        #if (-not $Items) { throw [System.NullReferenceException] '$Items cannot be null' }
        $breakdown = @()
        
        $_Items = @()

        function Categorical {
            param ($items, $property)

            $agg = @{}

            $item_collection = $items
            if ($property) { 
                $item_collection = $items.$property     
            }
            $total_count = 0
            $item_collection | foreach {
                $total_count++
                if ($agg.ContainsKey($_)) { $agg[$_] += 1 }
                else { $agg.Add($_, 1) }
            }
            $unique_items = $agg.Keys
        
            $breakdown += $unique_items | % { 
                $item_name = $_; 
                $this_item_count = $agg[$item_name]
                if ($this_item_count -eq 0) { $this_item_count = 1 }
                $pcnt = [Math]::Round(($this_item_count / $total_count) * 100, 2)
                New-Object psobject -Property @{"Item"=$item_name; "Count"=$this_item_count; "Percentage"=$pcnt}
            }
        
            $top = $breakdown | measure -Property Percentage -Maximum | select -ExpandProperty Maximum
    
            $breakdown | % {
                $skew = $_.Percentage/$top
                $bar = "$Visual" * [Math]::Ceiling($Scale * $skew)
                $_ | Add-Member -MemberType NoteProperty -Name Histogram -Value $bar
            }

            if ($Sort) {
                $breakdown = $breakdown | sort Count -Descending:$Descending
            }

            if ($breakdown_ref) {
                $breakdown_ref.Value = $breakdown
            }
            
            if ($ShowStats -and $PassThru -and -not $Verbose) {
                $_verbPre = $VerbosePreference            
                $VerbosePreference = [System.Management.Automation.ActionPreference]::Continue
                Write-Verbose "Total items: $total_count,  Unique items: $($breakdown.Count)"
                $VerbosePreference = $_verbPre        
            }
            if ($ShowStats -and -not $Verbose) {
                Write-Host "Total items: $total_count,  Unique items: $($breakdown.Count)"                
            }
            Write-Verbose "Total items: $total_count,  Unique items: $($breakdown.Count)"

            $breakdown | select Item, Count, Percentage, Histogram
        }

        function Numerical {
            param ($items, $property)
            [double]$min = [double]::MaxValue
            [double]$max = [double]::MinValue
            [double[]]$item_collection = @()
            if ($property) { [double[]]$item_collection = $items | Select-Object -ExpandProperty $property -ErrorAction SilentlyContinue | Where-Object { $_ } }
            else { [double[]]$item_collection = $items}
            $total_count = $item_collection.Count

            $max = [System.Linq.Enumerable]::Max($item_collection)
            $min = [System.Linq.Enumerable]::Min($item_collection)


            $range = 0
            if     ($min -lt 0) { $range = [Math]::Abs($min) + $max }
            elseif ($min -gt 0) { $range = $max - $min }
            elseif ($min -eq 0) { $range = $max - 0.1 }

            $bucket_size = $range / $BucketsCount
            $buckets = New-Object int[] $BucketsCount

            $zero_shift = $min * -1
            foreach ($n in $item_collection) {
                $offset = [Math]::Floor(($n + $zero_shift) / $bucket_size)
                if ($offset -ge $BucketsCount) {
                    $offset = $buckets.Count - 1
                }
                $buckets[$offset]++ 
            }
            $num_items = @()
            for ($i=0; $i -lt $BucketsCount; $i++) {
                $num_items += New-Object PSObject -Property @{
                    "Bucket"=$([Math]::Round($min + ($bucket_size * ($i+1)), 2));
                    "Count"=$buckets[$i]
                }
            }
        
            $breakdown += $num_items | % { 
                $i = $_; 
                $this_item_count = @($item_collection | ? { $_ -like $i }).Count
                if ($this_item_count -eq 0) { $this_item_count = 1 }
                $pcnt = [Math]::Round(($_.Count / $total_count) * 100, 2)
                $_ | Add-Member -MemberType NoteProperty -Name Percentage -Value $pcnt -PassThru
                }
        
            $top = $breakdown | measure -Property Percentage -Maximum | select -ExpandProperty Maximum
    
            $breakdown | % {
                $skew = $_.Percentage/$top
                $bar = "$Visual" * [Math]::Ceiling($Scale * $skew)
                $_ | Add-Member -MemberType NoteProperty -Name Histogram -Value $bar
            }
        
            if ($breakdown_ref) {
                $breakdown_ref.Value = $breakdown    
            }

            Write-Verbose "Min: $("{0:N2}" -f $min),  Max: $("{0:N2}" -f $max), Bucket Size: $("{0:N2}" -f $bucket_size)  Range: $("{0:N2}" -f $range)"
            if ($ShowStats -and -not $Verbose) {
                Write-Host "Min: $("{0:N2}" -f $min),  Max: $("{0:N2}" -f $max), Bucket Size: $("{0:N2}" -f $bucket_size)  Range: $("{0:N2}" -f $range)"
            }
        
            $breakdown | select Bucket, Count, Percentage, Histogram
        }
    }
    process {
        $_Items += $Items;
    }
    end {
        if ($Numerical) { Numerical $_Items $Property }
        else { Categorical $_Items $Property }
    }
}

return

<#
    Comment the former return statement to run this simple test.
    It demonstrates how to generate a histogram from the output
    of Get-ChildItem (do it in a directory with lots of files).
#>
cd /usr/local/bin  #change to fit your system
$files = gci
$histogram_data = $null
$files | Histogram 'Length' -Numerical
$files | Histogram 'Mode' -PassThru -ShowStats | Tee-Object -Variable 'histogram_data' | FT -AutoSize