How to sum multiple items in an object in PowerShell? - powershell

Question

I have:
$report.gettype().name
Object[]
echo $report
Item Average
-- -------
orange 0.294117647058824
orange -0.901960784313726
orange -0.901960784313726
grape 9.91335740072202
grape 0
pear 3.48736462093863
pear -0.0324909747292419
pear -0.0324909747292419
apple 12.1261261261261
apple -0.0045045045045045
I want to create a variable, $total, (such as a hash table) which contains the sum of the 'Average' column for each item, for example,
echo $total
orange -1.5097
grape 9.913
pear 3.423
apple 12.116
Right now I'm thinking of looping through the $report, but it's hell ugly, and I am looking for something more elegant than the following starting point (incomplete):
$tmpPrev = ""
foreach($r in $report){
$tmp = $r.item
$subtotal = 0
if($tmp <> $tmpPrev){
$subtotal += $r.average
}
How could I do this?

Answer 1

Cmdlets Group-Object and Measure-Object help to solve the task in a PowerShell-ish way:
Code:
# Demo input
$report = #(
New-Object psobject -Property #{ Item = 'orange'; Average = 1 }
New-Object psobject -Property #{ Item = 'orange'; Average = 2 }
New-Object psobject -Property #{ Item = 'grape'; Average = 3 }
New-Object psobject -Property #{ Item = 'grape'; Average = 4 }
)
# Process: group by 'Item' then sum 'Average' for each group
# and create output objects on the fly
$report | Group-Object Item | %{
New-Object psobject -Property #{
Item = $_.Name
Sum = ($_.Group | Measure-Object Average -Sum).Sum
}
}
Output:
Sum Item
--- ----
3 orange
7 grape

Answer 2

I've got a more command-line solution.
Given $report
$groupreport = $report | Group-Object -Property item -AsHashTable
is
Name Value
---- -----
grape {#{Item=grape; Average=9.91335740072202}, #{Item=grape; Average=0}}
orange {#{Item=orange; Average=0.294117647058824}, #{Item=orange; Average=-0.901960784313726...
apple {#{Item=apple; Average=12.1261261261261}, #{Item=apple; Average=-0.0045045045045045}}
pear {#{Item=pear; Average=3.48736462093863}, #{Item=pear; Average=-0.0324909747292419}, #...
then
$tab=#{}
$groupreport.keys | % {$tab += #{$_ = ($groupreport[$_] | measure-object -Property average -sum)}}
gives
PS> $tab["grape"]
Count : 2
Average :
Sum : 9,91335740072202
Maximum :
Minimum :
Property : Average
PS> $tab["grape"].sum
9,91335740072202
It seems short and usable.
Summary
$groupreport = $report | Group-Object -Property item -AsHashTable
$tab = #{}
$groupreport.keys | % {$tab += #{$_ = ($groupreport[$_] | measure-object -Property average -sum)}}
$tab.keys | % {write-host $_ `t $tab[$_].sum}

Answer 3

I don't know if you can get rid of looping. What about:
$report | % {$averages = #{}} {
if ($averages[$_.item]) {
$averages[$_.item] += $_.average
}
else {
$averages[$_.item] = $_.average
}
} {$averages}