从gnuplot中的数据文件中选择一行 [英] Selecting a single row from a data file in gnuplot

问题描述

我有一个包含100列和数千行的数据文件，但是我希望能够选择一个单行，在该行中，将偶数列用作X轴的输入，奇数列用作图的Y轴输入。有什么办法可以在gnuplot中实现？

I have a data file with 100 columns and thousands of rows, but I want to be able to select one single row, and in that row, use the even columns as the inputs for the X-axis and the odd columns as inputs for the Y-axis for a plot. Is there any way I can do that in gnuplot?

推荐答案

所以在这里，我完成了从一个给定的数据文件，其中奇数列为x轴，偶数列为y轴。

So here the script I've done to plot a given line from a given data file with odd column as x-axis and even column as y-axis.

#!/usr/bin/gnuplot
set term pdf
set output "plot.pdf"

line_number=1
data_file="data.dat"

set xrange[0:10]
set yrange[0:10]

table_file="/tmp/gnuplot_tab.dat"
set table table_file

plot for[i=1:*:2] "<(sed -n '".line_number."p' ".data_file.")" u i:i+1
unset table
unset key
plot table_file

让我们解释一下此脚本：

Let's explain this script:

首先，我们使用 line_number 指定行号，并使用 data_file 指定数据文件名。由gnuplot 设置表table_file 的效果是 nofollow noreferrer>文档，即在文件̀table_file 中打印点的坐标，而不是使用 plot`命令对其进行打印。

First we specify the line number with line_number and the data filename with data_file. The effect of set table table_fileis, as specified by gnuplot documentation, the print of points' coordinates in the file ̀table_fileinstead of ploting them withplot`command.

每个 i的[i = 1：*：2] 图的图从 1 开始，在无法绘制更多列并在以下位置增加 2 时结束每次迭代。想法是采用 i （ ie 奇数）和 i + 1 （ ie 偶数）作为坐标（或使用相反的 i + 1：i 取x轴为偶数，y轴为奇数）。

The plot for[i=1:*:2] plots for each i beginning from 1, ending when no more column can be ploted and incrementing by 2 at each iteration. The idea is to take the columns i (i.e. odd) and i+1 (i.e. even) as coordinates (or use the inverse i+1:i to take even for x-axis and odd for y-axis).

部分<（sed -n' .line_number。 p' .data_file。） 受 Gnuplot从文件向上绘制数据的启发到某行，然后选择您指定为文件的行。由于完成了设置表，因此此 plot 命令将每个坐标保存到一个新文件中。

The part "<(sed -n '".line_number."p' ".data_file.")" is inspired from Gnuplot plotting data from a file up to some row and selects the line you specified as a file. Since set table has been done, this plot command saves each coordinate to a new file. This is a trick to transform the line in a two column file.

最后，脚本禁用bset table ，然后绘制保存的文件

Finally the script disable the ̀set tableto then plot the saved filetable_file`

我用以下数据文件对其进行了测试，将行号从 1 更改为 2 ：

I tested it with the following data file changing the line number from 1 to 2:

10 10 9 9 8 8 7 7 6 6 5 5 4 4 3 3 2 2 1 1 0 0
0 10 1 9 2 8 3 7 4 6 5 5 6 4 7 3 8 2 9 1 10 0

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