在gnuplot中，在“缺少set datafile"的情况下，如何忽略两个"nan".和"-nan"? [英] In gnuplot, with "set datafile missing", how to ignore both "nan" and "-nan"?

问题描述

gnuplot命令set datafile missing "nan"告诉gnuplot忽略数据文件中的nan数据值.

The gnuplot command set datafile missing "nan" tells gnuplot to ignore nan data values in the data file.

如何同时忽略nan和-nan?我在gnuplot中尝试了以下内容，但是第一条语句的效果被下一条覆盖.

How to ignore both nan and -nan? I tried the following in gnuplot, but then the effect of the first statement is overwritten by the next.

gnuplot> set datafile missing "-nan"
gnuplot> set datafile missing "nan"

是否可以在gnuplot命令中甚至以某种方式将grep -v nan嵌入到某种regexp中，以排除任何可想象的非数值数据?

Is it possible to somewhow embed a grep -v nan in the gnuplot command, or even some kind of regexp to exclude any imaginable non-numerical data?

推荐答案

对于set datafile missing，不能使用正则表达式，但是您可以使用任何程序在绘图之前过滤数据，并用一个字符替换正则表达式，例如?设置为标记缺少的数据点.

It is not possible to use a regexp for set datafile missing, but you can use any program to filter you data before plotting, and replacing a regexp with one character, e.g. ? which you set to mark a missing data point.

这是一个完成您最初要求的示例:过滤-nan，inf等.为了进行测试，我使用了以下数据文件:

Here is an example which accomplishes, what you originally requested: filtering -nan, inf etc. For testing, I used the following data file:

1 0
2 nan
3 -inf
4 2
5 -NaN
6 1

并且绘图脚本可能如下所示:

And the plotting script may look like the following:

filter = 'sed -e "s/-\?\(nan\|inf\)/?/ig"'
set datafile missing "?"
set offset 0.5,0.5,0.5,0.5
plot '< '.filter.' data.txt' with linespoints ps 2 notitle

这将提供以下输出:

因此plot命令将跳过所有丢失的数据点.如果此变体不够大，则可以优化sed过滤器，以用?替换所有非数字值.

So the plot command skips all missing data points. You can refine the sed filter to replace any non-numerical values with ?, if this variant is not enough.

这很好用，但是只允许选择列，例如使用using 1:2，但不对列进行计算，例如using ($1*0.1):2.为此，您可以使用grep过滤出包含nan，-inf等的任何行，就像在中所做的一样gnuplot缺少具有表达式评估的数据(感谢@Thiru的链接):

This works fine, but allows only to select columns e.g. with using 1:2, but not doing computations on the columns, like e.g. using ($1*0.1):2. To allow this, you can filter out any row, which contains nan, -inf etc with grep, like its done in gnuplot missing data with expression evaluation (thanks @Thiru for the link):

filter = 'grep -vi -- "-\?\(nan\|inf\)"'
set offset 0.5,0.5,0.5,0.5
plot '< '.filter.' data.txt' with linespoints ps 2 notitle

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