Calculate number of ResourceGroups with same prefix string in name. (Microsoft Azure - Powershell)

NumberOfRG.ps1

$vmNamePrefix="SomeString"
$existingNumberOfRGs = $(Get-AzureRmResourceGroup | Where-Object {$_.ResourceGroupName -like "$vmNamePrefix*"}).count
$nextRGNumber = $existingNumberOfRGs + 1
$rgName = $rgNamePrefix + "$nextRGNumber"    

This gist is in powershell.
It takes a string as input.
Uses this string to find Resource Groups in Azure whose name starts with this string.
This is useful if name of RG is to be selected automatically.