Re: [Gnuplot-info] plot using 6:7:($10), how to perform math on the third entry??

[Thomas S. <t.s...@fz...>]

labels are strings, not numbers. the result of your calculation must be
a string:

plot 'datafile.txt' u 6:7:(sprintf("%f",-2.*$10)) index 1 w labels 


andreas oertel wrote:
> 
> Hi,
> 
> i am using GNUPLOT 4.5 under WinXP with the WXT terminal.
> 
> I have got files with data organized in columns divided in several blocks
> and want to plot the data values or calculations with them into the graph. 
> Lets say col 6 of the file contains X coordinates, col 7 the Y and col 10
> the data values.
> 
> I start to plot the data as label into the graph: plot 'datafile.txt' u
> 6:7:10 index 1 w labels -> works well.
> 
> Then i try to perform easy math on my data values: for example
> 
> plot 'datafile.txt' u 6:7:(-2.0*$10) index1 w labels 
> -> unfortunatly plot just returns the original data values, not the
> multiplication result.
> 
> second try:
> 
> f(x)=-2.0*x
> plot 'datafile.txt' u 6:7:(f($10)) index 1 w labels 
> -> same as above.
> 
> On the other hand: plot 'datafile.txt' u ($6+1):($7+1):10 index 1 w labels 
> -> shifts the coordinates as expected.
> 
> So how to perfom math operation on the third entry of the plot using
> clause or how to print values from calculations to the corresponding
> coordinates??
> 
> Thank you in advance,
> Andreas
> 
> 

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