Powershell CSV Import. Adding values together if username match

I have the following CSV file that I have imported into Powershell array

  User     Today  MTD
  ----     -----  ---
  User1    5      15
  User1    3      32
  User2    2      5
  User1    1      23
  User2    3      34
  User3    3      34

If the user matches I would like to add the Today and MTD figures to one line

Example: User1 would be "Today" 5+3+1=9 "MTD" 15+32+23=70

Required output:

  User     Today  MTD
  ----     -----  ---
  User1    9      70
  User2    5      39
  User3    3      34

I can list data for one username by using

$arr.Where({$_.User -eq "user1"})

But no idea how to add the today and MTD together

There you go, I answered a very similar question here.

Code:

$csv = @'
User,Today,MTD
User1,5,15
User1,3,32
User2,2,5
User1,1,23
User2,3,34
User3,3,34
'@ | ConvertFrom-Csv

$csv | Group-Object User | ForEach-Object {
    $_.Group[0].Today = ($_.Group.Today | Measure-Object -Sum).Sum
    $_.Group[0].MTD = ($_.Group.MTD | Measure-Object -Sum).Sum
    $_.Group[0]
}

Output:

User  Today MTD
----  ----- ---
User1     9  70
User2     5  39
User3     3  34

Edit

To export the results you can do this:

$csv | Group-Object User | ForEach-Object {
    # Original code here...
} | Export-Csv newCsv.csv -NoTypeInformation

Or this if you want to preserve the new object in memory:

$newCsv = $csv | Group-Object User | ForEach-Object {
    # Original code here...
}

$newCsv | Export-Csv newCsv.csv -NoTypeInformation