gnuplot:如何从顶点绘制多边形/轮廓 [英] Gnuplot: how to draw polygon/contour from its vertices

问题描述

我的data.txt文件包含形成多边形段的点的2D坐标.这些坐标随着时间的推移而发展.该文件的结构如下:

My data.txt file contains the 2D coordinates of points forming a segment of a polygon. These coordinates are evolving over time. The file is structured like this:

itr    nbr_pts   p1.x p1.y ...... pk.x pk.y
(itr+1) ..........
.....

其中，pk是多边形的第k个点/顶点，而nb_pts是顶点数.

where pk is the k-th point/vertex of the polygon and nb_pts is the number vertices.

我的问题是如何以一定的迭代次数(行)从其顶点(p1，p2，... pk)绘制2D多边形?

My question is how to draw the 2D polygon from its vertices (p1, p2, ...pk) at a certain iteration (row)?

此外，请注意，不仅有一个数据文件/多边形，还有N个:data1.txt .... dataN.txt

In addition, note that there is not only one data file/polygon but N ones: data1.txt .... dataN.txt

我尝试了类似的操作，但是没有用(Nbr个文件= 6)

I tried something like this but did not work (Nbr of files =6)

N = 6 
set multiplot
plot for [i=0:N-1]  polygon_i = sprintf("%s/data%d.dat",filename, i)  polygon_i val=$2 for [j=1:$2] u (j+1):(j+1+1)  w lines 

我知道有多少个多边形/文件(本例中为6个)，但是我对每个文件中的列数没有先验知识.顶点的数量可以从一个多边形到另一个多边形.

I know how many polygones/files there is (6 in this cae), but I have no prior knowledge on the number of columns in each file; the number of vertices can vary from a polygone to another.

请问有什么主意吗?

推荐答案

我的想法是需要对文件结构进行修改.对于每个迭代时间，都有一个包含多边形顶点的x和y坐标的块:

The idea I have would need a modification in the structure of your files. For each iteration time, there is a block containing the x and y coordinates of the polygon's vertices:

# file: data1.txt

# itr 0
0 0
1 1
1 2
0 0


# itr 1
1 3
2 1
0 1
1 2
1 3


# itr 2
3 1
2 1
0 0
3 1

请注意，每个块由两条空行分隔.对于迭代0(块0或itr 0)，存在具有三个顶点的多边形，itr 1具有四个顶点，而itr 2具有三个顶点.要获得闭合曲线，需要指定终点，例如，对于itr 1，我将点1 3放置两次.

Notice that each block is separated by two empty lines. For iteration 0 (block 0 or itr 0) there is a polygon with three vertices, itr 1 has four vertices, and itr 2 has three vertices. To obtain a closed curve, it is needed to specify the end point, for example, for itr 1 I put the point 1 3 twice.

对于此文件，我们可以在迭代iter中将多边形绘制为

For this file, we can plot the polygon at iteration iter as

iter = 1   # select block 1, or itr 1
plot "data1.txt" index iter w lp ps 2 pt 7 

如果您有多个文件，请尝试

If you have several files, then try

# option 1
nbr  = 6      # number of files
iter = 1      # select block 1, or itr 1

plot for [i=1:nbr] "data".i.".txt" index iter w lp ps 2 pt 7 title "".i

#option 2
files = system("ls data*.txt")   # get all datafiles in folder
iter = 1                         # select block 1, or itr 1

plot for [data in files] data index iter w lp ps 2 pt 7 title data

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