How to add different colors to one line chart

Question

Rizwan Khan 2020-9-14

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/593692-how-to-add-different-colors-to-one-line-chart

评论： Rizwan Khan 2020-9-16

采纳的回答： Vinicius Pereira Mateus Borges

I have a line plot, and i need it to change colour depending on some criteria.

I have the chart below, adn i want this charge to have different colors at different areas.

I've shown two charts below.

I want to change the colors of the top chart, depending on where the bottom chart is.

For eg. if the bottom chart is near 0, then show blue, if the bottom chart is up near 500 make the color of the top chart red, if the bottom chart is down near -500, then make the color of the top chart green.

All the documentation i've seen is about adding new lines with different colors, i don't want that, i want one line with multiple colors.

If someone can assist, that would be great.

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Adam Danz 2020-9-15

编辑：Adam Danz 2020-9-15

Here are two demos that produce what appears to be a single line with varying color.

https://www.mathworks.com/matlabcentral/answers/585011-how-could-i-adjust-the-color-of-multiple-lines-within-a-graph-without-using-the-default-matlab-colo#answer_485516

If you want to get into undocumented methods,

http://undocumentedmatlab.com/articles/plot-line-transparency-and-color-gradient

But one of the functions Walter Roberson mentioned is probably the easiest route for your task.

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Answer 1

Vinicius Pereira Mateus Borges 2020-9-15

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编辑：Vinicius Pereira Mateus Borges 2020-9-15

在 MATLAB Online 中打开

Hello Rizwan,

The plot you asked about seems to be using the scatter function instead of plot function in MATLAB.

The scatter function can take 3 arguments: the values of the x-axis, the values of the y-axis and the colormap of the dots. For example:

fakedata = cumsum( randn(1000, 1) );
depth = linspace(1,10,1000);
scatter(1:1000,fakedata,100,depth,'filled') % 100 relates to the size of each dot

Even though the data is just random numbers, the interpretation of such a graph is that there is a negative correlation between the x-axis and y-axis (as x values increase, y values tend to decrease) and the 'depth' represented by the colors also has a negative correlation with the y-axis (as the colors get hotter, i.e. increase in value, the y values tend to decrease).

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Rizwan Khan 2020-9-16

Thanks Both,

This is great, this is just what I needed.

Correct I asked for plot, but only because I didn't know other options existed, what I wanted was whatever solved the problem.

Thanks to both for your great feedback, truly appreciated

Rizwan Khan 2020-9-16

@Vinicius

Thanks to your help, i've been able to solve the problem, i wanted to share my results below:

Here is my stock data:

I then detrend the data, here is the detrended data

Then using your help, i scatter plot the stock data, using a colour map based on the detrended data as shown below

depth = detrend_sdata;

scatter(t,sdata,30,depth,'filled')

colorbar;

colormap jet;

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Answer 2

Walter Roberson 2020-9-14

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It is not possible in MATLAB for one Chart Line Object to have multiple colors.

For multiple colors you have a few possibilities:

multiple line objects
create a surface() with careful control over node colors and edge coloring configuration.
create a patch() with careful control over node colors and edge coloring configuration.

https://www.mathworks.com/matlabcentral/fileexchange/23566-3d-colored-line-plot

https://www.mathworks.com/matlabcentral/fileexchange/30423-conditionally-colored-line-plot

https://www.mathworks.com/matlabcentral/fileexchange/8597-plot-3d-color-line

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Walter Roberson 2020-9-15

You can use zero for the z.

So if i want to make a chart like below, its not possible?

It is not possible with a single Chart Line Object (more commonly known as a line() object.)

The underlying graphics system (OpenGL) that transforms coordinates into graphics, just does not support drawing multicolored lines as one of its "primitive" operations.

There are other ways to draw graphs like the one you picture -- but those ways do not involve using a single Chart Line Object.

Walter Roberson 2020-9-15

在 MATLAB Online 中打开

Using the first of the links I gave, color_line3:

color_line3(days, stock_price, zeros(size(stock_price)), detrended_stuff)

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