根据第三个值更改 2D 绘图线的颜色 [英] Change color of 2D plot line depending on 3rd value

问题描述

我有一个看起来像这样的数据集

I have a data set that looks like this

 140400 70.7850 1
 140401 70.7923 2
 140402 70.7993 3
 140403 70.8067 4
 140404 70.8139 5
 140405 70.8212 3

其中第一列对应于时间(数据点之间的一秒间隔)并将位于 x 轴上，第二列对应于距离并将位于 y 轴上.第三列是一个数字(一到五)，表示运动的限定条件.

Where the first column corresponds to time (one second intervals between data points) and will be on the x axis, the second column corresponds with distance and will be on the y axis. The third column is a number (one through five) that is a qualification of the movement.

我想绘制一个图，根据前一个数据点的数量改变两点之间的线的颜色.例如，我希望第一个和第二个数据点之间的线为红色，因为限定值为 1.

I want to make a plot that changes the color of the line between two points depending on what the number of the previous data point was. For example, I want the line to be red between the first and second data points because the qualification value was 1.

我看过很多关于根据强度值制作颜色滑动比例的帖子，但我只想要 5 种颜色:(红色、橙色、黄色、绿色和蓝色)分别.

I've seen a lot of posts about making a sliding scale of colors depending on an intensity value, but I just want 5 colors: (red, orange, yellow, green, and blue) respectively.

我尝试做这样的事情:

plot(x,y,{'r','o','y','g','b'})

但没有运气.

关于如何解决这个问题的任何想法?如果可能，不要循环.

Any ideas of how to approach this? Without looping if possible.

推荐答案

您也可以使用一个技巧来实现，该技巧适用于 2014b 之前的 Matlab 版本(至少可以追溯到 2009a).
但是，永远不会像您预期的那样简单(除非您为此处的解决方案之一编写包装器，否则您可以忘记 plot(x,y,{'r','o','y','g','b'})).

You can also do it with a trick which works with Matlab version anterior to 2014b (as far back as 2009a at least).
However, is will never be as simple as you expected (unless you write a wrapper for one of the solution here you can forget about plot(x,y,{'r','o','y','g','b'})).

诀窍是使用 surface 而不是 line 对象.表面受益于它们的 CData 属性和许多有用的功能来利用颜色贴图和纹理.

The trick is to use a surface instead of a line object. Surfaces benefit from their CData properties and a lot of useful features to exploit color maps and texture.

Matlab surf 不处理一维数据，它需要一个矩阵作为输入，所以我们将通过复制每个坐标集来给出它(例如 xx=[x,x]).
不过不用担心，表面会像线一样细，所以最终的结果并不难看.

Matlab surf does not handle 1D data, it needs a matrix as input so we are going to give it by just duplicating each coordinate set (for example xx=[x,x]).
Don't worry though, the surface will stay as thin as a line, so the end result is not ugly.

%% // your data
M=[140400 70.7850 1
 140401 70.7923 2
 140402 70.7993 3
 140403 70.8067 4
 140404 70.8139 5
 140405 70.8212 3];

x = M(:,1) ; %// extract "X" column
y = M(:,2) ; %// same for "Y"
c = M(:,3) ; %// extract color index for the custom colormap

%% // define your custom colormap
custom_colormap = [
    1  0 0 ; ... %// red
    1 .5 0 ; ... %// orange
    1  1 0 ; ... %// yellow
    0  1 0 ; ... %// green
    0  0 1 ; ... %// blue
    ] ;

%% // Prepare matrix data
xx=[x x];           %// create a 2D matrix based on "X" column
yy=[y y];           %// same for Y
zz=zeros(size(xx)); %// everything in the Z=0 plane
cc =[c c] ;         %// matrix for "CData"

%// draw the surface (actually a line)
hs=surf(xx,yy,zz,cc,'EdgeColor','interp','FaceColor','none','Marker','o') ;

colormap(custom_colormap) ;     %// assign the colormap
shading flat                    %// so each line segment has a plain color
view(2) %// view(0,90)          %// set view in X-Y plane
colorbar

<小时>

会得到你:

---

will get you:

举一个更一般的例子:

x=linspace(0,2*pi);
y=sin(x) ;

xx=[x;x];
yy=[y;y];
zz=zeros(size(xx));

hs=surf(xx,yy,zz,yy,'EdgeColor','interp') %// color binded to "y" values
colormap('hsv')
view(2) %// view(0,90)

会给你一个正弦波，颜色与 y 值相关联:

will give you a sine wave with the color associated to the y value:

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