Get a variable by dynamic variable name - powershell

Question

How does one access data imported from a CSV file by using dynamic note property names? That is, one doesn't know the colunm names beforehand. They do match a pattern and are extracted from the CSV file when the script runs.
As for an example, consider a CSV file:
"Header 1","Header A","Header 3","Header B"
0,0,0,0
1,2,3,4
5,6,7,8
I'd like to extract only columns that end with a letter. To do this, I read the header row and extract names with a regex like so,
$reader = new-object IO.StreamReader("C:\tmp\data.csv")
$line = $reader.ReadLine()
$headers = #()
$line.Split(",") | % {
$m = [regex]::match($_, '("Header [A-Z]")')
if($m.Success) { $headers += $m.value } }
This will get all the column names I care about:
"Header A"
"Header B"
Now, to access a CSV file I import it like so,
$csvData = import-csv "C:\tmp\data.csv"
Import-CSV will create a custom object that has properties as per the header row. One can access the fields by NoteProperty names like so,
$csvData | % { $_."Header A" } # Works fine
This obviously requires one to know the column name in advance. I'd like to use colunn names I extracted and stored into the $headers. How would I do that?
Some things I've tried so far
$csvData | % { $_.$headers[0] } # Error: Cannot index into a null array.
$csvData | % { $np = $headers[0]; $_.$np } # Doesn't print anything.
$csvData | % { $_.$($headers[0]) } # Doesn't print anything.
I could change the script like so it will write another a script that does know the column names. Is that my only solution?

Answer 1

I think you want this:
[string[]]$headers = $csvdata | gm -MemberType "noteproperty" |
?{ $_.Name -match "Header [a-zA-Z]$"} |
select -expand Name
$csvdata | select $headers
Choose the headers that match the condition (in this case, ones ending with characters) and then get the csv data for those headers.

Answer 2

the first thing ( and the only one... sorry) that came in my mind is:
$csvData | % { $_.$(( $csvData | gm | ? { $_.membertype -eq "noteproperty"} )[0].name) }
for get the first's column values and
$csvData | % { $_.$(( $csvData | gm | ? { $_.membertype -eq "noteproperty"} )[1].name) }
for second column and so on....
is this what you need?

Answer 3

you can use custom script to parse csv manually:
$content = Get-Content "C:\tmp\data.csv"
$header = $content | Select -first 1
$columns = $header.Split(",")
$indexes = #()
for($i; $i -lt $columns.Count;$i++)
{
# to verify whether string end with letter matches this regex: "[A-Za-z]$"
if ($column[$i] -match "[A-Za-z]$")
{
$indexes += $i
}
}
$outputFile = "C:\tmp\outdata.csv"
Remove-Item $outputFile -ea 0
foreach ($line in $content)
{
$output = ""
$rowcol = $line.Split(",")
[string]::Join(",", ($indexes | foreach { $rowcol[$_] })) | Add-Content $outputFile
}