Gnuplot CSV - 不同格式的数据

Question

I have a CSV file with data in this format:

Category        X-Axis  Y-Axis
Cat1            100     10.1
Cat1            101     10.12
Cat1            102     8.12

Cat2            100     11.1
Cat2            101     11.31
Cat2            102     12.11

Cat3            100     13.1

I would like to generate line graph using GNUplot, but GNUplot seems draw graph correctly only when data is cross-tabbed like this:

X-Axis      Cat1        Cat2        Cat3
100         10.1        11.1        13.1
101         10.12       11.31       13.2
102         8.12        12.11       13.3

The number of categories are not fixed, cross-tabbing will result in way too many categories will null/zero values.

Any suggestion to have GNUPlot draw line graphs without cross-tabbing data?

Answer 1

Make sure to separate each category by 2 or more blank lines.

Then plot with

plot "gnuplot.dat"  using 2:3:(column(-2)) linecolor variable with lines

This uses columns 2 and 3 for x, y respectively and the pseudo-column (column(-2)) . This is actually a reference to the distinct, internal index gnuplot gives to each data set.

You may want to check the detailed gnuplot help pages: within gnuplot enter help plot index .

Answer 2

If what you want is a distinct line with key/legend for each of your categories:

plot for [i=1:no_categories] datafile index i using 2:3 title "Cat".i

(make sure you have two empty lines between datasets, or use every )