Powershell Get-Random with Constraints - powershell

Question

I'm currently using the Get-Random function of Powershell to randomly pull a set number of rows from a csv. I need to create a constraint that says if one id is pulled, find the other ids that match it and pull their value.
Here is what I currently have:
$chosenOnes = Import-CSV C:\Temp\pk2.csv | sort{Get-Random} | Select -first 6
$i = 1
$count = $chosenOnes | Group-Object householdID
foreach ($row in $count)
{
if ($row.count -gt 1)
{
$students = $row.Group.Student
foreach ($student in $students)
{
$name = $student.tostring()
#...do something
$i = $i + 1
}
}
else
{
$name = $row.Group.Student
if($i -le 5)
{
#...do something
}
else
{
#...do something
}
$i = $i + 1
}
}
Example dataset
ID,name
165,Ernest Hemingway
1204,Mark Twain
1578,Stephen King
1634,Charles Dickens
1726,George Orwell
7751,John Doe
7751,Tim Doe
In this example, there are 7 rows but I'm randomly selecting 6 in my code. What needs to happen is when ID=7751 then I must return both rows where ID=7751. The IDs cannot not be statically set in the code.

Answer 1

Use Get-Random directly, with -Count, to extract a given number of random elements from a collection.
$allRows = Import-CSV C:\Temp\pk2.csv
$chosenHouseholdIDs = ($allRows | Get-Random -Count 6).householdID
Then filter all rows by whether their householdID column contains one of the 6 randomly selected rows' householdID values (PSv3+ syntax), using the -in array-containment operator:
$allRows | Where-Object householdID -in $chosenHouseholdIDs
Optional reading: performance considerations:
$allRows | Get-Random -Count 6 is not only conceptually simpler, but also much faster than $allRows | Sort-Object { Get-Random } | Select-Object -First 6
Using the Time-Command function to compare the performance of two approaches, using a 1000-row test file with 10 columns yields the following sample timings on my Windows 10 VM in Windows PowerShell - note that the Sort-Object { Get-Random }-based solution is more than 15(!) times slower:
Factor Secs (100-run avg.) Command TimeSpan
------ ------------------- ------- --------
1.00 0.007 $allRows | Get-Random -Count 6 00:00:00.0072520
15.65 0.113 $allRows | Sort-Object { Get-Random } | Select-Object -First 6 00:00:00.1134909
Similarly, a single pass through all rows to find matching IDs via array-containment operator -in performs much better than looping over the randomly selected IDs and searching all rows for each.

Answer 2

I tried sticking with your beginning and came up with this.
$Array = Import-CSV C:\test\StudtentTest.csv
$Array | Sort{Get-Random} | select -first 2 | %{
$id = $_.id
$Array | ?{$_.id -eq $id} | %{
$_
}
}
$Array will be your parsed CSV
We pipe in and sort by random select -first 2 (in this case)
Save the ID of the object into $id and then search the array for that ID and dispaly each that matches
If same ID does match you end up with something like
ID name
-- ----
7751 John Doe
7751 Tim Doe
1634 Charles Dickens