Hi Friends,
It was a tough time to find the PowerShell or a C# API to enable or disable Rating/Likes Settings in SharePoint 2013. I found a helpful post from Nanddeep for c# equivalent. I have converted it in PowerShell, hope this will help some of SharePoint developers and admins.
Add-PSSnapin "Microsoft.SharePoint.PowerShell" -ErrorAction SilentlyContinue.
$web=Get-SPWeb "http://abc.com/test";
$list=$web.Lists["Pages"];
if($list -ne $null)
{
Write-Host $list.Title "not null";
$assembly=[System.Reflection.Assembly]::Load("Microsoft.SharePoint.Portal, Version=15.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c")
$reputationHelper =$assembly.GetType("Microsoft.SharePoint.Portal.ReputationHelper");
$bindings = @("EnableReputation", "NonPublic", "Static");
[System.Reflection.BindingFlags]$flags = [System.Reflection.BindingFlags]::Static -bor [System.Reflection.BindingFlags]::NonPublic;
$methodInfo = $reputationHelper.GetMethod("EnableReputation", $flags);
#For enabling Ratings
$values = @($list, "Ratings", $false);
#OR for enabling Likes
#$values = @($list, "Likes", $false);
$methodInfo.Invoke($null, @($values));
#For disable Rating or Likes
<#$methodInfo = $reputationHelper.GetMethod("DisableReputation", $flags);
$disableValues = @($list);
$methodInfo.Invoke($null, @($disableValues));#>
}