How to plot it?

Question

Ara 2022-7-13

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1758660-how-to-plot-it

评论： Ara 2022-7-16

采纳的回答： Chunru

Dear All,

We have

a=1,2,3,4,5; (in a column 1)

b=-1000,10,0,20,-20; (in a column 2)

b_filtered=b(:,2)>=0;

plot (a,b_filtered);

How to plot these two values that after filtered they have two different dimensions?

Best,

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Answer 1

Chunru 2022-7-13

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a = [1,2,3,4,5];

b = [-1000,10,0,20,-20];

idx = b>=0;

plot(a(idx), b(idx), 'o-');

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Chunru 2022-7-16

plot(a.a(idx,1), a.a(idx,2), 'o-');

Ara 2022-7-16

Thank you.

your plot is different with the other answeres. I do not know which one is correct to adapt it to my code. Do you know?

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Answer 2

Mathieu NOE 2022-7-13

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hello

simply replace the negative values of b by NaN so the vector size remains the same

a=[1;2;3;4;5];
b= [-10;10;0;20;-20]; 
b_filtered=b;
b_filtered(b<0) = NaN; 
plot (a,b,a,b_filtered,'dr');

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Mathieu NOE 2022-7-13

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hello

both answers are correct and will display the exact same plot

I wanted to have both b and b_filtered the same size as a , because it seemed to me that you wanted it this way.

the other options as suggested by @Chunru works also , and if you want to have both b and b_filtered displayed , you can slightly modify his code :

it's up to you to pick the one you prefer

a = [1,2,3,4,5];        
b = [-10,10,0,20,-20];  
idx = b>=0;
plot(a,b,a(idx), b(idx), 'or');

Ara 2022-7-16

Hello Mathieu,

The plot you provided is different with the plot above provided by another expert who response to my question. I am confuse as I do not know which one is correct and how to modify my code based on which solution. Would you please tell me which one is correct?

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Answer 3

Ruchika P Barman 2022-7-13

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It is my understanding that you are trying to plot a and b_filtered. I believe b_filtered is supposed to contain the non-negative elements of b, please correct me if I'm wrong on this, I did not understand what exactly is (b(:,2)>=0) supposed to do? If I'm not wrong, we can retain the elements of a at the indices where b is not negative and plot a and b accordingly.

a=[1;2;3;4;5];

b= [-10;10;0;20;-20];

b(b<0)=NaN;

a(b<0)=NaN;

b_filtered=b;

p=plot (a,b_filtered,"red");

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Answer 4

Ara 2022-7-13

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Thank you Ruchika, for your response.

it means second column of my data should be greater than zero. I do not know which answer is correct as the figure for second answer isnot the same with yours. You and the first answer are the same output.

I have to modify it in a large set of data.

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Ara 2022-7-14

Hello,

I meant second column of b, which is a column with many data.

Ara 2022-7-15

编辑：Ara 2022-7-15

I have "data" file. When I open it in matlab that consist of 12 coumns and one of them is b. So, b is a column that contain a full range of data in a one column.

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