PowerShell - nucleotide-count

powershell/nucleotide-count/NucleotideCount.ps1

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+Function Get-NucleotideCount() {
+    <#
+    .SYNOPSIS
+    Given a single stranded DNA string, compute how many times each nucleotide occurs in the string.
+    
+    .DESCRIPTION
+    The genetic language of every living thing on the planet is DNA.
+    DNA is a large molecule that is built from an extremely long sequence of individual elements called nucleotides.
+    4 types exist in DNA and these differ only slightly and can be represented as the following symbols: 'A' for adenine, 'C' for cytosine, 'G' for guanine, and 'T' thymine.
+
+    The function counts the occurances of A, C, G and T in the supplied strand. It then outputs in the format:
+
+    A:0, C:0, G:0, T:0
+    
+    .PARAMETER Strand
+    The DNA strand to count
+    
+    .EXAMPLE
+    Get-NucleotideCount -Strand "ACGTAGCTT"
+    
+    Retuns: A:2 C:2 G:2 T:3
+    #>
+    [CmdletBinding()]
+    Param(
+        [string]$Strand
+    )
+
+    if ($Strand -notmatch "^[ACGT]*$") {
+        Throw "Invalid DNA Strand"
+    }
+
+    $counts = @{"A" = 0; "C" = 0; "G" = 0; "T" = 0}
+    foreach ($char in $Strand.ToCharArray()) { $counts[$char.ToString()] += 1 }
+
+    return "A:$($counts['A']) C:$($counts['C']) G:$($counts['G']) T:$($counts['T'])"
+}