How to plot it?

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,

Answer 1

[Chunru]

a = [1,2,3,4,5];        
b = [-1000,10,0,20,-20];  
idx = b>=0;
plot(a(idx), b(idx), 'o-');

[Ara]

Thank you for your response.

What if, a and b are written like this a.a(:,1), a.a(:,2). Should be written like this?

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

[Chunru]

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

[Ara]

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?

Answer 2

[Mathieu NOE]

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');

[Ara]

Thank you for your reply.

The plot based on your code is different with the above answer? So, I am not sure, which one is the correct one.

[Mathieu NOE]

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]

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?

Answer 3

[Ruchika P Barman]

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");

Answer 4

[Ara]

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.

[Ruchika P Barman]

Hello, @Ara.

Do you mean 'b' by 'second column of my data' or second column of 'b' which is a single element i.e 10? If it is the former, then the output from both the answers are correct.

Please let me know if I can help you further, thank you.

[Ara]

Hello,

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

[Ara]

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.