Gnuplot:数据归一化 [英] Gnuplot: data normalization

问题描述

我有几个规模非常不同的基于时间的数据集，例如g.

I have several time-based datasets which are of very different scale, e. g.

[set 1]
2010-01-01  10
2010-02-01  12
2010-03-01  13
2010-04-01  19
…

[set 2]
2010-01-01  920
2010-02-01  997
2010-03-01  1010
2010-04-01  1043
…

自2010年1月1日以来，我想绘制两者的相对增长情况.要将两条曲线放在同一张图上，我必须对其进行归一化.因此，我基本上需要选择第一个Y值并将其用作权重:

I'd like to plot the relative growth of both since 2010-01-01. To put both curves on the same graph I have to normalize them. So I basically need to pick the first Y value and use it as a weight:

plot "./set1" using 1:($2/10), "./set2" using 1:($2/920)

但是我想自动执行此操作，而不是硬编码10和920作为分隔符.我什至不需要第二列的最大值，我只想选择第一个值，或者最好是给定日期的值.

But I want to do it automatically instead of hard-coding 10 and 920 as dividers. I don't even need the max value of the second column, I just want to pick the first value or, better, a value for a given date.

所以我的问题是:有没有一种方法可以对给定列的值进行参数化，该值对应于给定X列的给定值(X是时间轴)?像

So my question: is there a way to parametrize the value of a given column which corresponds a given value of the given X column (X is a time axis)? Something like

plot "./set1" using 1:($2/$2($1="2010-01-01")), "./set2" using 1:($2/$2($1="2010-01-01"))

其中$ 2($ 1 ="2010-01-01")是我要的功能.

where $2($1="2010-01-01") is the feature I'm looking for.

推荐答案

选择第一个值非常容易.只需记住它的值并用它除以所有数据值即可:

Picking the first value is quite easy. Simply remember its value and divide all data values by it:

ref = 0
plot "./set1" using 1:(ref = ($0 == 0 ? $2 : ref), $2/ref),\
     "./set2" using 1:(ref = ($0 == 0 ? $2 : ref), $2/ref)

更需要使用给定日期的值:

Using the value at a given date is more involved:

使用外部工具(awk)

ref1 = system('awk ''$1 == "2010-01-01" { print $2; exit; }'' set1')
ref2 = system('awk ''$1 == "2010-01-01" { print $2; exit; }'' set1')
plot "./set1" using 1:($2/ref1), "./set1" using 1:($2/ref2)

使用gnuplot

您可以使用gnuplot的 stats 命令选择所需的值，但是您必须注意在此之后进行所有时间设置:

You can use gnuplot's stats command to pick the desired value, but you must pay attention to do all time settings only after that:

a)字符串比较

stats "./set1" using (strcol(1) eq "2010-01-01" ? $2 : 1/0)
ref1 = STATS_max
...
set timefmt ...
set xdata time 
...
plot ...

b)比较实际时间值(仅从版本5.0开始如此工作):

b) Compare the actual time value (works like this only since version 5.0):

reftime = strptime("%Y-%m-%d", "2010-01-01")
stats "./set1" using (timecolumn(1, "%Y-%m-%d") == reftime ? $2 : 1/0)
ref1 = STATS_max
...
set timefmt ...
set xdata time 
...
plot ...

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