Automating process to multiply values in tab delimited file by -1 to negate them

I've been manually processing a large amount of files in Excel. I've done some searching but haven't found a definitive best practice as to how I can achieve this process in an automated fashion.

My manual process is as follows:

I have a .tab (Tab-delimited) file. There are a total of 8 "columns" for each row. I need to negate the numerical values in the last 5 columns of every row.

What I've been doing

Open the file in Excel
Type a -1 in any blank cell. Copy it
Highlight the data in the last 5 columns → right-click → Paste Special → Multiply → Enter
Then save the file.

I'm not sure if the best approach for this is going to be PowerShell or an alternative script, so I wanted to reach out to the community to see what advice others may have for this. Thank you for your time.

In PowerShell you can use Import-Csv for reading and Export-Csv for writing character-delimited files. Both cmdlets provide a parameter -Delimiter that allows you to specify the delimiter character:

$csv = Import-Csv 'C:\path\to\input.csv' -Delimiter "`t"
$csv | Export-Csv 'C:\path\to\output.csv' -Delimiter "`t" -NoType

Importing a CSV via Import-Csv gives you a list of custom objects where each field from the CSV is represented as a property of the object. You modify the fields by modifying the values of the properties before writing the data back to a file. To do this you can take either of the following two approaches:

Read the CSV completely into a variable, update the fields you want to modify in a loop, then export the data back to a file:
```
$csv = Import-Csv ...
foreach ($row in $csv) {
  [int]$row.B *= -1
  [int]$row.F *= -1
}
$csv | Export-Csv ...
```
Read the CSV into a pipeline and replace the fields you want to modify via calculated properties:
```
Import-Csv ... |
  Select-Object -Include *,@{n='B';e={-$_.B}},@{n='F';e={-$_.F}} -Exclude B,F |
  Export-Csv ...
```
Note that for this to work you must either use separate input and output files, or put the Import-Csv statement in parentheses. Otherwise Export-Csv would fail, because it can't write to the CSV while Import-Csv is still reading from it.

You can credit a button that's on your sheet anywhere you want that can run this macro. Assuming you know the basics of a macro/VBA (if you don't let me know) and A1 = -1 (can change in the below script).

Range("A1").Select
ActiveCell.FormulaR1C1 = "-1"
Range("B1:F1").Select
Range(Selection, Selection.End(xlDown)).Select
Range("A1").Select
Selection.Copy
Range("B1:F1").Select
Range(Selection, Selection.End(xlDown)).Select
Selection.PasteSpecial Paste:=xlPasteAll, Operation:=xlMultiply, _
    SkipBlanks:=False, Transpose:=False

来源：https://stackoverflow.com/questions/39980639/automating-process-to-multiply-values-in-tab-delimited-file-by-1-to-negate-them

标签

excel

powershell

negate