Compare two csv entries in powershell - powershell

Question

I'm just learning powershell, but have run up on this error that has me stumped. The objective is to take a csv file and ascertain how many groups there are in the file. There will be multiple entries under each group. The end result would be to split the file into different arrays/dictionaries/whathaveyou (i started with powershell 3hrs ago..) based on the groups, keeping the TaxonIDs intact, then export those to separate files. But for now, I'm just at the comparison step.
My practice data look like
Group,TaxonID
AA,1
AA,2
BB,3
BB,4
and true data look like:
Group,TaxonID
Bilateria_Ropsin,Mus_musculus_Rhabdomeric_MEL
Bilateria_Ropsin,ROp_OG3TodaroP
To do this, I tried to compare the group in one row with the group in the next row. if they differ, then I add one to a variable for later use. Here's what i've got to do the comparison:
Set-Variable -name book -value C:\Users\XXX\Documents\Book1.csv
$work = Import-Csv $book
$numgroups = 0
$i=0
foreach ($Group in $work) {
$Ogroup = $work[$i] | select-object{$_.Group}
$nextGroup = $work[$i+1] | select-object{$_.Group}
$compare = $Ogroup.Equals($nextGroup)
$compare
$i++
}
When i print out $Ogroup and $nextGroup, they give me the proper pairs (AA AA, AA BB, BB BB), but $compare always prints out false. Using Compare-Object gives me an error about $nextGroup being null..so I opted for using .Equals(). CompareTo() throws an error about it not being a valid method.
I'm stumped and need help.

Answer 1

You shoud use Group-Object CmdLet
Set-Variable -name book -value C:\Users\XXX\Documents\Book1.csv
$work = Import-Csv $book
$groups = $work | Group-Object -Property Group
$groups.count
$groups[0].name
$groups[0].Group[0]
for ($i=0 ; $i -lt $groups.count ; $i++) { $groups[$i].name}
for ($i = 0 ; $i -lt $groups.count ; $i++)
{
$groups[$i].name;
for ($j=0 ; $j -lt $groups[$i].count;$j++)
{
$groups[$i].group[$j]
}
}

Answer 2

Comparing isn't needed. Split the groups out first:
$book = "$env:USERPROFILE\Documents\Book1.csv"
$work = Import-CSV $book
$Groups = $work | Group-Object Group
ForEach($Group in $Groups){
"Group Name: "+$Group.name
"Taxon IDs: "
$Group.group.TaxonID
}
If you want to save each group to a file, within that ForEach loop you can do $Group|export-csv "c:\path\$($Group.name).csv" -notypeinfo
Edit: Sorry, was working on an answer when security called me over the intercom and said a water main burst under my truck and they needed me to go move my vehicle. Figured not losing my vehicle to a sinkhole was more important than this.