13

I have a data file that lists hits and misses for a certain cache system. Following is the data file format

time hits misses
1 12 2
2 34 8
3 67 13
...

To plot a 2D graph in GNUPlot for time vs hits, the command would be:

plot "data.dat" using 1:2 using lines

Now I want to plot a graph of time vs hit-ratio, For this can I do some computation for the second column like :

plot "data.dat" using 1:2/ (2 + 3) using lines

Here 1, 2, 3 represent the column number.

Any reference to these kind of graph plotting will also be appreciated.

Thanks in advance.

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2 Answers 2

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18

What you have is almost correct. You need to use $ symbols to indicate the column in the calculation:

plot "data.dat" using 1:($2/($2 + $3))

Since you are using $n to refer to the column numbers, you now are able to use n to refer to the number itself. For example, 

plot "data.dat" using 1:(2 * $2)

will double the value in the second column.

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2 Comments

Thank you! Could you also tell me if I want to multiply a certain column by say 5, what will be the command?
@Swaranga Sarma Edited the answer to include an example. I used 2 instead of 5, to emphasize that column numbers and literals can be used together without problem.
5

In general, you can even plot C functions like log and cos of a given column. For example:

plot "data.dat" u 1:(exp($2))

Note the parens on the outside of the argument that uses the value of a particular column.

See here for more info.

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