I have two arrays in Powershell:
$headings = ['h1', 'h2']
$values = [3, 4]
It is guaranteed that both arrays have the same length. How can I create an array where the values of $headings become the headings of the $values array?
I want to be able to do something like this:
$result['h2'] #should return 4
Update:
The arrays $headings and $values are of type System.Array.
As stated above you'll need a PowerShell hashtable. By the way array in PowerShell are defined via #(), see about_arrays for further information.
$headings = #('h1', 'h2')
$values = #(3, 4)
$combined = #{ }
if ($headings.Count -eq $values.Count) {
for ($i = 0; $i -lt $headings.Count; $i++) {
$combined[$headings[$i]] = $values[$i]
}
}
else {
Write-Error "Lengths of arrays are not the same"
}
$combined
Dumping the content of combined returns:
$combined
Name Value
---- -----
h2 4
h1 3
Try something like this :
$hash = [ordered]#{ h1 = 3; h2 = 4}
$hash["h1"] # -- Will give you 3
## Next Approach
$headings = #('h1', 'h2') #array
$values = #(3, 4) #array
If($headings.Length -match $values.Length)
{
For($i=0;$i -lt $headings.Length; $i++)
{
#Formulate your Hashtable here like the above and then you would be able to pick it up
#something like this in hashtable variable $headings[$i] = $values[$i]
}
}
PS: I am just giving you the logical headstart and helping you with the hashtable part. Code is upto you.
Related
I want to find indexes of repeated values in array.
E.g.
Input:
$data = #(1, 2, 3, 2, 1)
Output:
$indexes = #(3, 4)
For a different approach, you can use try-catch blocks with a hash table.
$data = #(1, 2, 3, 2, 1)
$hash = #{}
$indexes = for ($i = 0; $i -lt $data.count; $i++ ) {
try {
$hash.add($data[$i],$i)
}
catch {
$i
continue
}
}
# Output
$indexes
3
4
The idea here is to add each value as a key and the corresponding index as a value to the hash table. Since a [hashtable] object can only have unique keys, an exception will be thrown and caught. In the catch block, we just output the index which is ultimately stored in $indexes. The continue statement allows the loop to increment and keep processing.
Algorithmically speaking this solution is almost identical to the already proposed solution. However, it utilizes the more efficient Add() method of [arraylist] rather than rebuilding (+=) an [array] during each iteration. The performance is negligible in this example but could be worth considering in larger data sets. This also opts for the traditional for loop rather than foreach.
$uniqueValues = [collections.arraylist]#()
$indexes = for ($i = 0; $i -lt $data.count; $i++) {
if ($uniqueValues -contains $data[$i]) {
$i
}
else {
[void]$uniqueValues.Add($data[$i])
}
}
# Output
$indexes
3
4
This solution maintains an [arraylist] of unique values ($uniqueValues). Any value that is not unique, its index ($i) is output and stored in $indexes. Uniqueness is determined by using the -contains operator to compare the current value in the $data iteration to what is already in $uniqueValues.
You could also use a Hashtable for this:
$data = 1, 2, 3, 2, 1
$hash = #{}
$indexes = for ($i = 0; $i -lt $data.Count; $i++) {
# the value you store in the $hash in the else block is not important
if ($hash.ContainsKey($data[$i])) { $i } else {$hash[$data[$i]] = $true}
}
$indexes
Result:
3
4
Foreach loop with if inside should do the job:
$data = #(1, 2, 3, 2, 1)
$uniqueValues = #()
$duplicatesIndexes = #()
$data | ForEach-Object {$counter = 0}{
if ($_ -notin $uniqueValues) {
$uniqueValues += $_
} else {
$duplicatesIndexes += $counter
}
$counter++
}
# Output
PS> $duplicatesIndexes
3
4
I'm writing a script to fetch values for a set of components and storing the fetched values in an array. As there are many components I created a loop and tried to create an array name along with its iteration value (fi1, fi2, fi3, etc.) like this.
Here is the code:
function fiswitchinfo {
Param ($sheet, [string]$text, $iter)
$($fi+($iter)) = #()
$max = $sheet.UsedRange.Rows.Count
for ($i=1; $i -lt 900 ; $i++) {
$rows = $sheet.Cells.Item($i, 2).EntireRow
$cell_info = $sheet.Cells.Item($i, 2)
$cell = $cell_info.Address($false, $false)
if ($rows.hidden -eq $false) {
$cell_info = $sheet.Cells.Item($i, 2).Text
if ($cell_info -ne "" -and $cell_info.Contains($text) -eq "True") {
$cell = $cell -split "(?<=[A-Z])(?=\d)"
[int]$curline = $cell[1]
$component = $sheet.Cells.Item($curline, 2).Text
$compip = $sheet.Cells.Item($curline, 3).Text
$row = $sheet.Cells.Item($curline, 2).EntireRow
$cellinfo = $sheet.Cells.Item($curline, 2).text
if ($row.Hidden -ne "True" -and $cellinfo -ne $null) {
Write-Host $component $compip
$script:fi+$iter += $compip
}
}
}
}
}
fiswitchinfo $worksheet_3 "Fabric Interconnect 01 Cluster IP" 1
fiswitchinfo $worksheet_3 "Fabric Interconnect 01 A" 1
fiswitchinfo $worksheet_3 "Fabric Interconnect 01 B" 1
I'm not quite sure what you expect $($fi+($iter)) or $script:fi+$iter to do, but I'm pretty certain they won't do whatever it is you expect.
To have a function create an array of arrays in a loop and then return it you'd do something like this:
function fiswitchinfo {
...
$arr = #()
for ($i=1; $i -lt 900 ; $i++) {
...
$arr += ,$compip
}
return ,$arr
}
$fi1 = fiswitchinfo ...
$fi2 = fiswitchinfo ...
...
The leading comma in the statements $arr += ,$compip and return ,$arr is the unary array construction operator, which prevents PowerShell from unrolling the arrays. $arr += ,$compip appends $compip to $arr as a nested array (thus making $arr a jagged array) instead of appending the elements of $compip to $arr. return ,$arr ensures that $arr is returned to the caller as-is (thus preserving the array even if it's empty).
I'd like to join two arrays by picking the elements from each array one by one. and not have them combined or simply merged
I know how to add a second array to the first one as in:
$array1 = (0,4,8)
$array2 = (1,5,2)
$array1 += $array2
$array1
Which results in the following:
0
4
8
1
5
2
But how can I copy them into one another giving me an output like this:
0
1
4
5
8
2
Note: I don't want to merge them and then sort the list.
The elements need to stay in the same order. How would that be achieved?
Although Esperento57 gives you a perfect working solution, here's my idea that will also allow for arrays that are not of the same length. It uses a System.Collections.ArrayList to add the values from the arrays for better performance if you have large arrays to combine.
$array1 = (0,2,4)
$array2 = (1,3,5,6,7,8)
$len1 = $array1.Length
$len2 = $array2.Length
$maxLength = [Math]::Max($len1, $len2)
$listResult = New-Object System.Collections.ArrayList
for ($i = 0; $i -lt $maxLength; $i++) {
if ($i -lt $len1) { [void] $listResult.Add($array1[$i]) }
if ($i -lt $len2) { [void] $listResult.Add($array2[$i]) }
}
$listResult.ToArray()
try something like this
$array1 = (0,2,4)
$array2 = (1,3,5)
$MaxLen=[Math]::Max($array1.Length, $array2.Length)
$Result=#()
for ($i = 0; $i -lt $MaxLen; $i++)
{
$Result+=$array1[$i]
$Result+=$array2[$i]
}
$Result
here's another way to do it. [grin]
this one takes into account dissimilar sizes in the arrays and interleaves them until one array runs out of items. the remaining items in the larger array are then added without "ghost" items from the the smaller array.
$array1 = #(0,2,4)
$array2 = #(5,7,9,11)
$InterleavedArray = [System.Collections.Generic.List[int]]::new()
$UpperBound = [math]::Max($array1.GetUpperBound(0), $array2.GetUpperBound(0))
foreach ($Index in 0..$UpperBound)
{
if ($Index -le $array1.GetUpperBound(0))
{
$InterleavedArray.Add($array1[$Index])
}
if ($Index -le $array2.GetUpperBound(0))
{
$InterleavedArray.Add($array2[$Index])
}
}
$InterleavedArray
output ...
0
5
2
7
4
9
11
hope that helps,
lee
If you want the elements to stay in the same order, just do $array3 = $array1 + $array2. If you want to sort it though, do $array3 = ($array1 + $array2) | sort.
Here is a slightly modified version of Theos answer.
Looks cleaner and its faster:
$array1 = (0,2,4)
$array2 = (1,3,5,6,7,8)
$len1 = $array1.Length
$len2 = $array2.Length
$maxIndex = [Math]::Max($len1, $len2)-1
$arrayResult = #()
$arrayResult = foreach ($i in 0..$maxIndex) {
if ($i -lt $len1) { $array1[$i] }
if ($i -lt $len2) { $array2[$i] }
}
$arrayResult
Q: I'm looking for a more elegant way to get the closest match of a numerical from an array.
I may have over-complicated things here
Input
## A given array A where to search in
$a = (16/10),(16/9),(4/3),(5/4),(21/10),(21/9)
## A given value B which should be searched for in array A (closest match)
$b = 16/11
Desired output
"Closest value to 16/11 is 4/3"
My current code to solve the problem
## New array C for the differences of array A - B
$c = $a | %{ [math]::abs($_ - $b) }
## Measure array C to get lowest value D
$d = $c | measure -Minimum
## Get position E of value D in array C
$e = [array]::IndexOf($c, $d.minimum)
## Position E correlates to array A
echo "Closest value to $b is $($a[$e])
Remarks
It don't has to be an array if a hash table or something else suits better
My current code outputs decimals like 1.33333 instead of fractions 4/3. It would be nice to output the fraction
Short code is always better
$a = (16/10),(16/9),(4/3),(5/4),(21/10),(21/9)
$b = 16/11
$oldval = $b - $a[0]
$Final = $a[0]
if($oldval -lt 0){$oldval = $oldval * -1}
$a | %{$val = $b - $_
if($val -lt 0 ){$val = $val * -1}
if ($val -lt $oldval){
$oldval = $val
$Final = $_} }
Write-host "$Final is the closest to $b"
$diff = $b - $a[0]
$min_index = 0
for ($i = 1; $i -lt $a.count; $i++)
{
$new_diff = $b - $a[$i]
if ($new_diff -lt $diff)
{
$diff = $new_diff
$min_index = $i
}
}
Write-Output "Closest value to $b is $($a[$min_index])"
Powershell dose not support fraction values...
## A given array A where to search in
$a = '16/10','16/9','4/3','5/4','21/10','21/9'
## A given value B which should be searched for in array A (closest match)
$b = '16/11'
$numericArray = ($a | % { Invoke-Expression $_ })
$test = Invoke-Expression $b
$best = 0
$diff = [double]::MaxValue
for ($i = 1; $i -lt $numericArray.count; $i++) {
$newdiff = [math]::abs($numericArray[$i] - $test)
if ($newdiff -lt $diff) {
$diff = $newdiff
$best = $i
}
}
"Closest value to $b is $($a[$best])"
The big difference here is that the inputs are strings and not numbers, so we can preserve the fractions.
Security note: Don't use this if the inputs are from a user, as passing user-generated strings to Invoke-Expression is obviously a recipe for trouble.
## A given array A where to search in
$a = (16/10),(16/9),(4/3),(5/4),(21/10),(21/9)
## A given value B which should be searched for in array A (closest match)
$b = 16/11
<#Create a new-Object , we'll use this to store the results in the Foreach Loop#>
$values = [Pscustomobject] #{
'result' = #()
'a-values' = #()
}
foreach($aa in $a)
{ #round to 2 decimal places and then subtract
#store the result at the 'a-value' used to create that result
$values.result += [MATH]::Abs( [Math]::Round($B,2)`
-[Math]::Round($aa,2)`
)
$values."a-values" += $aa
}
# sort ascending and then this gets me the number closest to Zero
$lookFor = $($values.result | Sort-Object )[0]
#the result of the Number closest to $b = 16/11
$endresult = $values.'a-values'[ $values.result.indexof($lookfor) ]
Write-host "the number closest to '$b' is '$endresult'"
Remove-Variable values
Here's a oneliner sorting with distance function:
($a | Sort-Object { [Math]::abs($_ - $b) })[0]
Returning a fraction is not possible in this case because e.g. 16/10 is immediately converted to a decimal.
I want to fill up a dynamic array with the same integer value as fast as possible using Powershell.
The Measure-Command shows that it takes 7 seconds on my system to fill it up.
My current code (snipped) looks like:
$myArray = #()
$length = 16385
for ($i=1;$i -le $length; $i++) {$myArray += 2}
(Full code can be seen on gist.github.com or on superuser)
Consider that $length can change. But for better understanding I chose a fixed length.
Q: How do I speed up this Powershell code?
You can repeat arrays, just as you can do with strings:
$myArray = ,2 * $length
This means »Take the array with the single element 2 and repeat it $length times, yielding a new array.«.
Note that you cannot really use this to create multidimensional arrays because the following:
$some2darray = ,(,2 * 1000) * 1000
will just create 1000 references to the inner array, making them useless for manipulation. In that case you can use a hybrid strategy. I have used
$some2darray = 1..1000 | ForEach-Object { ,(,2 * 1000) }
in the past, but below performance measurements suggest that
$some2darray = foreach ($i in 1..1000) { ,(,2 * 1000) }
would be a much faster way.
Some performance measurements:
Command Average Time (ms)
------- -----------------
$a = ,2 * $length 0,135902 # my own
[int[]]$a = [System.Linq.Enumerable]::Repeat(2, $length) 7,15362 # JPBlanc
$a = foreach ($i in 1..$length) { 2 } 14,54417
[int[]]$a = -split "2 " * $length 24,867394
$a = for ($i = 0; $i -lt $length; $i++) { 2 } 45,771122 # Ansgar
$a = 1..$length | %{ 2 } 431,70304 # JPBlanc
$a = #(); for ($i = 0; $i -lt $length; $i++) { $a += 2 } 10425,79214 # original code
Taken by running each variant 50 times through Measure-Command, each with the same value for $length, and averaging the results.
Position 3 and 4 are a bit of a surprise, actually. Apparently it's much better to foreach over a range instead of using a normal for loop.
Code to generate above chart:
$length = 16384
$tests = '$a = ,2 * $length',
'[int[]]$a = [System.Linq.Enumerable]::Repeat(2, $length)',
'$a = for ($i = 0; $i -lt $length; $i++) { 2 }',
'$a = foreach ($i in 1..$length) { 2 }',
'$a = 1..$length | %{ 2 }',
'$a = #(); for ($i = 0; $i -lt $length; $i++) { $a += 2 }',
'[int[]]$a = -split "2 " * $length'
$tests | ForEach-Object {
$cmd = $_
$timings = 1..50 | ForEach-Object {
Remove-Variable i,a -ErrorAction Ignore
[GC]::Collect()
Measure-Command { Invoke-Expression $cmd }
}
[pscustomobject]#{
Command = $cmd
'Average Time (ms)' = ($timings | Measure-Object -Average TotalMilliseconds).Average
}
} | Sort-Object Ave* | Format-Table -AutoSize -Wrap
Avoid appending to an array in a loop. It's copying the existing array to a new array with each iteration. Do this instead:
$MyArray = for ($i=1; $i -le $length; $i++) { 2 }
Using PowerShell 3.0 you can use (need .NET Framework 3.5 or upper):
[int[]]$MyArray = ([System.Linq.Enumerable]::Repeat(2, 65000))
Using PowerShell 2.0
$AnArray = 1..65000 | % {2}
It is not clear what you are trying. I tried looking at your code. But, $myArray +=2 means you are just adding 2 as the element. For example, here is the output from my test code:
$myArray = #()
$length = 4
for ($i=1;$i -le $length; $i++) {
Write-Host $myArray
$myArray += 2
}
2
2 2
2 2 2
Why do you need to add 2 as the array element so many times?
If all you want is just fill the same value, try this:
$myArray = 1..$length | % { 2 }
If you need it really fast, then go with ArrayLists and Tuples:
$myArray = New-Object 'Collections.ArrayList'
$myArray = foreach($i in 1..$length) {
[tuple]::create(2)
}
and if you need to sort it later then use this (normally a bit slower):
$myArray = New-Object 'Collections.ArrayList'
foreach($i in 1..$length) {
$myArray.add(
[tuple]::create(2)
)
}
both versions are in the 20ms range for me ;-)