extracting x,y data from certain time points in matrix?

Question

nines 2021-7-25

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/885524-extracting-x-y-data-from-certain-time-points-in-matrix

评论： nines 2021-7-26

采纳的回答： Image Analyst

在 MATLAB Online 中打开

Hello!

I have the txt file that looks as follows:

x y

Where the first column is time and the second column is a changing value y.

I want to extract all the x,y values where x<=10 and x>= 5, e.g.

As of now the code I am using is (where srtm is the first code box above):

x = find(srtm(:, 1)> 5 & srtm(:,1) < 20)

and that just gives me the corresponding column numbers (4, 5, 6, 7, 8, 9), but not at x values.

My question is:

1) how to I extract the x, y coordinates from a matrix where x=> number1, x=<number2?

Thanks so much for all of your help!

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Image Analyst 2021-7-25

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/885524-extracting-x-y-data-from-certain-time-points-in-matrix#answer_753504

在 MATLAB Online 中打开

Instead of

x = find(srtm(:, 1)> 5 & srtm(:,1) < 20)

to do masking from 5 to 10 inclusive, you need to change x to indexes, 20 to 10, and use <= and <=

x = srtm(:, 1);
y = srtm(:, 2);
% Find linear indexes in the range [5, 10].
indexes = find(x >= 5 & x <= 10) % Or could use logical indexes, like: indexes = x >= 5 & x <= 10
% Extract values in that range ONLY.
xm = x(indexes);
ym = y(indexes);
plot(xm, yb, 'b.-', 'LineWidth', 2, 'MarkerSize', 20);