How to switch to this graph? Mathematical question

Question

Elia Paini 2021-11-3

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1578320-how-to-switch-to-this-graph-mathematical-question

评论： Star Strider 2021-11-6

采纳的回答： Star Strider

Hi, I have a bit complicated question about a way to obtain a graph from a set of data.

I have a code that return a solution of three variables, related to solving a system of several equations.

For example, Matlab output is like the following:

a = [1 0.2 0.2];

b = [0 0.4 0.4];

c = [0 0.4 0.4]; which are plotted on distance x = [0 0.5 1];

a, b, c represent three volume fractions, with the constraint that sum over a column is 1 (on the left of the figure).

However, for an easier understanding, I need a graphic representation showing not the absolute values of those fractions, but their distribution (on the right).

I know it's likely a "mathematical question" than "Matlab question", but I don't know how to proceed.

I need an appliable strategy on any solution, not this one in particular.

Thanks for your help!!

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Answer 1

Star Strider 2021-11-3

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1578320-how-to-switch-to-this-graph-mathematical-question#answer_823105

在 MATLAB Online 中打开

Try this —

x = [0 0.5 1];

a = [1 0.2 0.2];

b = [0 0.4 0.4];

c = [0 0.4 0.4];

figure

patch([x flip(x)], [c zeros(size(c))], 'g', 'FaceAlpha',0.75)

hold on

patch([x flip(x)], [b ones(size(a))], 'r', 'FaceAlpha',0.75)

patch([x flip(x)], [b flip(a+c)], 'b', 'FaceAlpha',0.75)

hold off

text([1 1 1]*0.8, [0.2 0.5 0.8], compose('%c',['c','a','b']), 'FontWeight','bold')

.

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Star Strider 2021-11-4

在 MATLAB Online 中打开

A more robust approach would be to use the area function, creating the matrix by vertically concatenating the vectors in the order in which they are to be plotted, and then transposing the resulting matrix (noting that the area function plots across the columns, not the rows as in most other graphics functions so that the plotted lines correspond to the ‘CalculateYcoordinates’ matrix) —

x = [0 0.5 1];

a = [1 0.2 0.2];

b = [0 0.4 0.4];

c = [0 0.4 0.4];

abc = [c; a; b]' % Note The Concatenation Order & Subsequent Transposition

abc = 3×3

0 1.0000 0 0.4000 0.2000 0.4000 0.4000 0.2000 0.4000

CalculateYcoordinates = cumsum(abc,2) % Information Only To Demonstrate What The 'area' Funciton Plots, Not Required For The Code

CalculateYcoordinates = 3×3

0 1.0000 1.0000 0.4000 0.6000 1.0000 0.4000 0.6000 1.0000

figure

area(x, abc)

text([1 1 1]*0.8, [0.2 0.5 0.8], compose('%c',['c','a','b']), 'FontWeight','bold')

That approach should work for similar problems with different [c,a,b] vectors and ‘abc’ matrices.

.

Elia Paini 2021-11-6

Yes, this is exactly what I need! It works for any vectors, and the display order is optional.

Thank you!!

Star Strider 2021-11-6

As always, my pleasure!

.

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Answer 2

Alan Stevens 2021-11-3

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https://ww2.mathworks.cn/matlabcentral/answers/1578320-how-to-switch-to-this-graph-mathematical-question#answer_823085

在 MATLAB Online 中打开

Try:

plot(x,c,x,1-b)

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Elia Paini 2021-11-3

编辑：Elia Paini 2021-11-3

This is correct, there's only one problem.

This can be coupled only to this easy example. Actually, solution can be very complex, also with 50 points for every variable. The example I considered is very easy, with only three points and regular lines.

My question is not about that problem, I asked for a single code which can be applied to every case.

I hope you understand me.

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