Convert text string file to object array without outputting to file first?

Question

I have a log file that is just a text string file which is appended to with Out-File.  If the log file does not exist I pipe headers to it so that I can import the data as CSV.  For example:
DATA.LOG
DATE,TIME,RESPONSE_TIME
05-28-2014, 14:47, 132
05-28-2014, 14:50, 94
05-28-2014, 14:53, 72
I'm using Microsoft Chart Controls to graph the data; it takes it in via CSV format.  If I'm going to chart all the entries in DATA.LOG I can simply IMPORT-CSV DATA.LOG.  But I only want to graph the 20 most recent entries.
Perhaps there is a better way to do this, but to maintain the header and get the 20 most recent entries I'm using select.
$DATA+=Get-Content .\data.log | select -first 1
$DATA+=Get-Content .\data.log | select -last 20
The problem is $DATA is of type system string so I can't use it directly with Chart Controls; I need to get it in CSV format first.  I can Out-File $DATA and then use IMPORT-CSV.  But I'd prefer to not have to use
the temporary file.  Any suggestions on how I can accomplish this objective? 

Answer 1

Import-CSV creates an object with the 'header' becoming the named values in the array.  The code I posted does the same thing as your 4 lines of code in one line of code:
Much more quickly:
PS C:\temp> (1..1000 | measure-command {import-csv .\data.log | select -last 2}).totalseconds
0.4792951
PS C:\temp> (1..1000 | measure-command {$DATATMP=@();$DATATMP+=Get-Content .\data.log | select -first 1;$DATATMP+=Get-Content .\data.log | select -last 2;ConvertFrom-CSV $DATATMP}).totalseconds
1.6227726
You're more than welcome to use whatever code you want, but if you want to improve your Powershell knowledge you should try to understand the object model around which Powershell is built, it is powerful and efficient.
I hope this post has helped!