# Comparing two multi-dimensional arrays **URL:** \ **Category:** PowerShell Help\ **Created:** [July 1, 2015, 5:50am UTC](https://forums.powershell.org/t/comparing-two-multi-dimensional-arrays/4455 "2015-07-01T05:50:15Z")\ **Posts on this page:** 15\ **Page:** 1
**Author:** ![dan-trimpey](https://avatars.discourse-cdn.com/v4/letter/d/54ee81/32.png) [@dan-trimpey](https://forums.powershell.org/u/dan-trimpey)\ **Post date:** [July 1, 2015, 5:50am UTC](https://forums.powershell.org/t/comparing-two-multi-dimensional-arrays/4455/1 "2015-07-01T05:50:15Z")
I’m trying to come up with the most efficient way to compare two arrays where there could be any number of columns in each array, but we are matching on a specified column from each array. I want to retain all data from each array. Some arrays could contain duplicates. I am finding that when I compare arrays with more than a few thousand lines, the compare can start to take a long time, over an hour in some cases. Is my Compare Function the most efficient way to do this? Here is my sample code: Function RJ-CombinedCompare() { [CmdletBinding()] PARAM([Parameter(Mandatory=$True)]$List1,$L1Match,$List2,$L2Match) $List = $List1 | %{[PSCustomObject]@{L1Data = $_; L2Data = ‘NA’}} $List += $List2 | %{[PSCustomObject]@{L1Data = ‘NA’; L2Data = $_}} foreach ($Object in $List.L1Data.$L1Match + $List.L2Data.$L2Match | select -Unique) { $Match1 = @() $Match2 = @() foreach ($Object1 in $List.L1Data -ne ‘NA’) { if ($Object1.$L1Match -eq $Object) {$Match1 += $Object1} } foreach ($Object2 in $List.L2Data -ne ‘NA’) { if ($Object2.$L2Match -eq $Object) {$Match2 += $Object2} } [PSCustomObject]@{MatchValue = $Object; L1Matches = $Match1.count; L2Matches = $Match2.count; List1 = $Match1; List2 = $Match2} } } $List1 = @( [PSCustomObject]@{Alias = 1; Place = 1; Extra = ‘c’} [PSCustomObject]@{Alias = 2; Place = 3; Extra = ‘a’} [PSCustomObject]@{Alias = 3; Place = 2; Extra = ‘c’} [PSCustomObject]@{Alias = 4; Place = 1; Extra = ‘a’} [PSCustomObject]@{Alias = 22; Place = 3; Extra = ‘g’} [PSCustomObject]@{Alias = 2; Place = 3; Extra = ‘a’} [PSCustomObject]@{Alias = 5; Place = 6; Extra = ‘e’} [PSCustomObject]@{Alias = 4; Place = 2; Extra = ‘c’} [PSCustomObject]@{Alias = 1; Place = 6; Extra = ‘b’} ) $List2 = @( [PSCustomObject]@{Name = 1; Place = 5; Somthing = ‘a1’} [PSCustomObject]@{Name = 1; Place = 1; Somthing = ‘b6’} [PSCustomObject]@{Name = 5; Place = 1; Somthing = ‘c3’} [PSCustomObject]@{Name = 2; Place = 4; Somthing = ‘a3’} [PSCustomObject]@{Name = 12; Place = 6; Somthing = ‘a1’} [PSCustomObject]@{Name = 1; Place = 2; Somthing = ‘b1’} [PSCustomObject]@{Name = 2; Place = 7; Somthing = ‘d4’} [PSCustomObject]@{Name = 44; Place = 2; Somthing = ‘a5’} ) $Result = RJ-CombinedCompare -List1 $List1 -L1Match Alias -List2 $List2 -L2Match Name ---
**Author:** ![rob-simmers](https://sea1.discourse-cdn.com/flex019/user_avatar/forums.powershell.org/rob-simmers/32/1010_2.png) [@rob-simmers](https://forums.powershell.org/u/rob-simmers)\ **Post date:** [July 1, 2015, 6:37am UTC](https://forums.powershell.org/t/comparing-two-multi-dimensional-arrays/4455/2 "2015-07-01T06:37:53Z")
Have you looked at Compare-Object? ``` $List1 = @( [PSCustomObject]@{Alias = 1; Place = 1; Extra = 'c'} [PSCustomObject]@{Alias = 2; Place = 3; Extra = 'a'} [PSCustomObject]@{Alias = 3; Place = 2; Extra = 'c'} [PSCustomObject]@{Alias = 4; Place = 1; Extra = 'a'} [PSCustomObject]@{Alias = 22; Place = 3; Extra = 'g'} [PSCustomObject]@{Alias = 2; Place = 3; Extra = 'a'} [PSCustomObject]@{Alias = 5; Place = 6; Extra = 'e'} [PSCustomObject]@{Alias = 4; Place = 2; Extra = 'c'} [PSCustomObject]@{Alias = 1; Place = 6; Extra = 'b'} ) $List2 = @( [PSCustomObject]@{Name = 1; Place = 5; Somthing = 'a1'} [PSCustomObject]@{Name = 1; Place = 1; Somthing = 'b6'} [PSCustomObject]@{Name = 5; Place = 1; Somthing = 'c3'} [PSCustomObject]@{Name = 2; Place = 4; Somthing = 'a3'} [PSCustomObject]@{Name = 12; Place = 6; Somthing = 'a1'} [PSCustomObject]@{Name = 1; Place = 2; Somthing = 'b1'} [PSCustomObject]@{Name = 2; Place = 7; Somthing = 'd4'} [PSCustomObject]@{Name = 44; Place = 2; Somthing = 'a5'} ) Compare-Object -ReferenceObject $List1 -DifferenceObject $List2 -Property Place ``` ---
**Author:** ![dan-trimpey](https://avatars.discourse-cdn.com/v4/letter/d/54ee81/32.png) [@dan-trimpey](https://forums.powershell.org/u/dan-trimpey)\ **Post date:** [July 1, 2015, 7:16am UTC](https://forums.powershell.org/t/comparing-two-multi-dimensional-arrays/4455/3 "2015-07-01T07:16:31Z")
Thanks for the response, That works to some degree, but it doesn’t seem to maintain all the columns from each array. Can that be done with Compare-Object? E.g: Compare-Object -ReferenceObject $List1 -DifferenceObject $List2 -Property Place -IncludeEqual Place SideIndicator * * * 1 == 1 == 2 == 6 == 2 == 5 =\> 4 =\> 7 =\> 3 \<= 3 \<= 3 \<= 6 \<= With my Function, each Array's content is preserved in the result: RJ-CombinedCompare -List1 $List1 -L1Match Place -List2 $List2 -L2Match Place | ft MatchValue L1Matches L2Matches List1 List2 * * * 1 2 2 {@{Alias=1; Place=1; … {@{Name=1; Place=1; S… 3 3 0 {@{Alias=2; Place=3; … {} 2 2 2 {@{Alias=3; Place=2; … {@{Name=1; Place=2; S… 6 2 1 {@{Alias=5; Place=6; … {@{Name=12; Place=6; … 5 0 1 {} {@{Name=1; Place=5; S… 4 0 1 {} {@{Name=2; Place=4; S… 7 0 1 {} {@{Name=2; Place=7; S… ---
**Author:** ![max-kozlov](https://avatars.discourse-cdn.com/v4/letter/m/50afbb/32.png) [@max-kozlov](https://forums.powershell.org/u/max-kozlov)\ **Post date:** [July 1, 2015, 5:42pm UTC](https://forums.powershell.org/t/comparing-two-multi-dimensional-arrays/4455/4 "2015-07-01T17:42:49Z")
Dan, your way absolutely ineffective, because you combine both arrays in beginning (for what reason? ) `$List = $List1 | %{[PSCustomObject]@{L1Data = $; L2Data = ‘NA’}} $List += $List2 | %{[PSCustomObject]@{L1Data = ‘NA’; L2Data = $}}` and later _never_ use it in combined form, but several times filter it for original arrays: `$Object in $List.L1Data.$L1Match +$List.L2Data.$L2Match ` `foreach ($Object1 in $List.L1Data -ne ‘NA’) {` `if ($Object1.$L1Match -eq $Object) {$Match1 += $Object1}` and so on. The code below 3 times more effective even on your sample. and should be more effective on large arrays. Btw, tell me how much… ``` #Require -Version 4.0 Function RJ-CombinedCompare() { [CmdletBinding()] PARAM( #Every parameter must be mandatory [Parameter(Mandatory=$True)]$List1, [Parameter(Mandatory=$True)]$L1Match, [Parameter(Mandatory=$True)]$List2, [Parameter(Mandatory=$True)]$L2Match) #Fill HASH with arrays of data from both arrays, hash keys is value to compare $hash = @{} foreach ($data in $List1) { $hash[$data.$L1Match] += ,$data } foreach ($data in $List2) { $hash[$data.$L2Match] += ,$data } # filter every hash value by existance of $L1Match field in data. # {$_.$L1Match} - subject to change if $L1Match property exists in both $List1 and $List2 # or may be $null foreach ($kv in $hash.GetEnumerator()) { $m1, $m2 = $kv.Value.where( {$_.$L1Match}, 'Split') [PSCustomObject]@{ MatchValue = $kv.Key L1Matches = $m1.Count L2Matches = $m2.Count List1 = $m1 List2 = $m2 } } } $List1 = @( [PSCustomObject]@{Alias = 1; Place = 1; Extra = 'c'} [PSCustomObject]@{Alias = 2; Place = 3; Extra = 'a'} [PSCustomObject]@{Alias = 3; Place = 2; Extra = 'c'} [PSCustomObject]@{Alias = 4; Place = 1; Extra = 'a'} [PSCustomObject]@{Alias = 22; Place = 3; Extra = 'g'} [PSCustomObject]@{Alias = 2; Place = 3; Extra = 'a'} [PSCustomObject]@{Alias = 5; Place = 6; Extra = 'e'} [PSCustomObject]@{Alias = 4; Place = 2; Extra = 'c'} [PSCustomObject]@{Alias = 1; Place = 6; Extra = 'b'} ) $List2 = @( [PSCustomObject]@{Name = 1; Place = 5; Somthing = 'a1'} [PSCustomObject]@{Name = 1; Place = 1; Somthing = 'b6'} [PSCustomObject]@{Name = 5; Place = 1; Somthing = 'c3'} [PSCustomObject]@{Name = 2; Place = 4; Somthing = 'a3'} [PSCustomObject]@{Name = 12; Place = 6; Somthing = 'a1'} [PSCustomObject]@{Name = 1; Place = 2; Somthing = 'b1'} [PSCustomObject]@{Name = 2; Place = 7; Somthing = 'd4'} [PSCustomObject]@{Name = 44; Place = 2; Somthing = 'a5'} ) RJ-CombinedCompare -List1 $List1 -L1Match Alias -List2 $List2 -L2Match Name #Speed measurement measure-command { 1..10000 | %{ $Result = RJ-CombinedCompare -List1 $List1 -L1Match Alias -List2 $List2 -L2Match Name } } ``` ---
**Author:** ![max-kozlov](https://avatars.discourse-cdn.com/v4/letter/m/50afbb/32.png) [@max-kozlov](https://forums.powershell.org/u/max-kozlov)\ **Post date:** [July 1, 2015, 5:50pm UTC](https://forums.powershell.org/t/comparing-two-multi-dimensional-arrays/4455/5 "2015-07-01T17:50:27Z")
should warn You that in my code List1 and List2 in result objects is not arrays but collections. But may be You do not even notice the difference 🙂 ---
**Author:** ![dan-trimpey](https://avatars.discourse-cdn.com/v4/letter/d/54ee81/32.png) [@dan-trimpey](https://forums.powershell.org/u/dan-trimpey)\ **Post date:** [July 2, 2015, 1:39am UTC](https://forums.powershell.org/t/comparing-two-multi-dimensional-arrays/4455/6 "2015-07-02T01:39:21Z")
Hi Max, Thanks so much for your assistance. In my tests, your Function is extremely fast. The only issue I am having is when I run the compare where I am Matching on columns that have the same name, in the result its combining the result into list 1. I’m trying to see how I can modify your Function to handle that case. E.g.: ``` RJ-CombinedCompare -List1 $List1 -L1Match Place -List2 $List2 -L2Match Place | ft MatchValue L1Matches L2Matches List1 List2 ---------- --------- --------- ----- ----- 7 1 0 {@{Name=2; Place=7; Somthing=d4}} {} 6 3 0 {@{Alias=5; Place=6; Extra=e}, @... {} 5 1 0 {@{Name=1; Place=5; Somthing=a1}} {} 4 1 0 {@{Name=2; Place=4; Somthing=a3}} {} 3 3 0 {@{Alias=2; Place=3; Extra=a}, @... {} 2 4 0 {@{Alias=3; Place=2; Extra=c}, @... {} 1 4 0 {@{Alias=1; Place=1; Extra=c}, @... {} ``` ---
**Author:** ![max-kozlov](https://avatars.discourse-cdn.com/v4/letter/m/50afbb/32.png) [@max-kozlov](https://forums.powershell.org/u/max-kozlov)\ **Post date:** [July 2, 2015, 6:39pm UTC](https://forums.powershell.org/t/comparing-two-multi-dimensional-arrays/4455/7 "2015-07-02T18:39:12Z")
You can save data owner as `$hash[$data.$L1Match] += ,[pscustomobject]@{Owner=‘l1’;Value=$data }` and for List2 too use it here `$m1, $m2 = $kv.Value.where( {$_.Owner -eq ‘l1’}, ‘Split’)` but then need to modify result assinging: `List1 = $m1.Value` I do not test it, correct any erors if i make it 🙂 ---
**Author:** ![max-kozlov](https://avatars.discourse-cdn.com/v4/letter/m/50afbb/32.png) [@max-kozlov](https://forums.powershell.org/u/max-kozlov)\ **Post date:** [July 2, 2015, 6:45pm UTC](https://forums.powershell.org/t/comparing-two-multi-dimensional-arrays/4455/8 "2015-07-02T18:45:18Z")
for owner better use [bool] or [int] identifier, not a [string], I use it only for information purposes ---
**Author:** ![dan-trimpey](https://avatars.discourse-cdn.com/v4/letter/d/54ee81/32.png) [@dan-trimpey](https://forums.powershell.org/u/dan-trimpey)\ **Post date:** [July 7, 2015, 4:32am UTC](https://forums.powershell.org/t/comparing-two-multi-dimensional-arrays/4455/9 "2015-07-07T04:32:05Z")
Thanks for all you help Max. Here’s the final Function. It’s a lot more than 3 times faster, my large compare went from 45min to 5 seconds! ``` Function RJ-CombinedCompare() { [CmdletBinding()] PARAM( #Every parameter must be mandatory [Parameter(Mandatory=$True)]$List1, [Parameter(Mandatory=$True)]$L1Match, [Parameter(Mandatory=$True)]$List2, [Parameter(Mandatory=$True)]$L2Match ) #Fill HASH with arrays of data from both arrays, hash keys is value to compare $hash = @{} foreach ($data in $List1) {$hash[$data.$L1Match] += ,[pscustomobject]@{Owner='l1';Value=$($data)}} foreach ($data in $List2) {$hash[$data.$L2Match] += ,[pscustomobject]@{Owner='l2';Value=$($data)}} # filter every hash value by existance of $L1Match field in data. # {$_.$L1Match} - subject to change if $L1Match property exists in both $List1 and $List2 # or may be $null foreach ($kv in $hash.GetEnumerator()) { $m1, $m2 = $kv.Value.where({$_.Owner -eq 'l1'}, 'Split') [PSCustomObject]@{ MatchValue = $kv.Key L1Matches = $m1.Count L2Matches = $m2.Count L1MatchObject = $L1Match L2MatchObject = $L2Match List1 = $m1.Value List2 = $m2.Value } } } ``` ---
**Author:** ![max-kozlov](https://avatars.discourse-cdn.com/v4/letter/m/50afbb/32.png) [@max-kozlov](https://forums.powershell.org/u/max-kozlov)\ **Post date:** [July 8, 2015, 8:30pm UTC](https://forums.powershell.org/t/comparing-two-multi-dimensional-arrays/4455/10 "2015-07-08T20:30:17Z")
Congrats! 🙂 but change everywhere ‘l1’ and ‘l2’ to 1 and 2, it save you some more execution time and memory eliminating string allocation. It’s already memory hungry. ---
**Author:** ![dan-trimpey](https://avatars.discourse-cdn.com/v4/letter/d/54ee81/32.png) [@dan-trimpey](https://forums.powershell.org/u/dan-trimpey)\ **Post date:** [July 9, 2015, 7:19am UTC](https://forums.powershell.org/t/comparing-two-multi-dimensional-arrays/4455/11 "2015-07-09T07:19:04Z")
Thank you Sir! Its done: ``` Function RJ-CombinedCompare() { [CmdletBinding()] PARAM( [Parameter(Mandatory=$True)]$List1, [Parameter(Mandatory=$True)]$L1Match, [Parameter(Mandatory=$True)]$List2, [Parameter(Mandatory=$True)]$L2Match ) $hash = @{} foreach ($data in $List1) {$hash[$data.$L1Match] += ,[pscustomobject]@{Owner='1';Value=$($data)}} foreach ($data in $List2) {$hash[$data.$L2Match] += ,[pscustomobject]@{Owner='2';Value=$($data)}} foreach ($kv in $hash.GetEnumerator()) { $m1, $m2 = $kv.Value.where({$_.Owner -eq '1'}, 'Split') [PSCustomObject]@{ MatchValue = $kv.Key L1Matches = $m1.Count L2Matches = $m2.Count L1MatchObject = $L1Match L2MatchObject = $L2Match List1 = $m1.Value List2 = $m2.Value } } } ``` ---
**Author:** ![pscookiemonster](https://sea1.discourse-cdn.com/flex019/user_avatar/forums.powershell.org/pscookiemonster/32/634_2.png) [@pscookiemonster](https://forums.powershell.org/u/pscookiemonster)\ **Post date:** [July 9, 2015, 8:11am UTC](https://forums.powershell.org/t/comparing-two-multi-dimensional-arrays/4455/12 "2015-07-09T08:11:43Z")
Hello there! A short while back, I borrowed some code from Lucio Silveira (MSFT) and Dave Wyatt (superstar) and duct taped together [a modified Join-Object](http://ramblingcookiemonster.github.io/Join-Object/). That link walks through using it in a number of scenarios. It has quickly becomer one of the ‘most-used’ functions in my PowerShell toolbox. Cheers! ---
**Author:** ![max-kozlov](https://avatars.discourse-cdn.com/v4/letter/m/50afbb/32.png) [@max-kozlov](https://forums.powershell.org/u/max-kozlov)\ **Post date:** [July 9, 2015, 7:52pm UTC](https://forums.powershell.org/t/comparing-two-multi-dimensional-arrays/4455/13 "2015-07-09T19:52:35Z")
Dan, be more watchful 🙂 you sould replace Owner=‘1’; to Owner=1; _Without quotes!_ to convert owner field from [string] to [int] and of course **$_.Owner -eq ‘1’_** _to **$** _ **.Owner -eq _1_** and if you gonna more faster use arraylist, instead of array as in Join-Object. that modification get more time, but lit learn you well, if you need 🙂 because each = ,obj assignment recreates new array ---
**Author:** ![nickm](https://avatars.discourse-cdn.com/v4/letter/n/58f4c7/32.png) [@nickm](https://forums.powershell.org/u/nickm)\ **Post date:** [September 16, 2016, 2:36am UTC](https://forums.powershell.org/t/comparing-two-multi-dimensional-arrays/4455/14 "2016-09-16T02:36:00Z")
The code works perfectly on v5. When running it on v3 I get the following exception: ``` Method invocation failed because [System.Management.Automation.PSCustomObject] doesn't contain a method named 'where'. + $m1, $m2 = $kv.Value.where({$_.Owner -eq 1}, 'Split') ``` How can I re-write the line ``` $m1, $m2 = $kv.Value.where({$_.List -eq 1}, 'Split') ``` to run it on v3 without changing the functionality? (Installing v5 ist not possible.) ---
**Author:** ![dotnVo](https://avatars.discourse-cdn.com/v4/letter/d/4af34b/32.png) [@dotnVo](https://forums.powershell.org/u/dotnVo)\ **Post date:** [May 16, 2024, 8:40pm UTC](https://forums.powershell.org/t/comparing-two-multi-dimensional-arrays/4455/15 "2024-05-16T20:40:19Z")