Calculations on every 2nd row in a matrix in sets of 2 rows

Question

Alex Hughes 2020-9-16

0
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https://ww2.mathworks.cn/matlabcentral/answers/594652-calculations-on-every-2nd-row-in-a-matrix-in-sets-of-2-rows

评论： Alex Hughes 2020-9-16

I have a matrix of x and y points with 2 columns and n number of rows.

The first column is the x data (distance) and the 2nd coloumn is the y data (height (or depth in this case as they are underwater)). Each row represents a specific point on a topographic profile relating to either the top or bottom of a scarp so every two rows define the top and bottom of a specific scarp i.e., row 1 represents the top of a scarp and row 2 represents the bottom. Row 3 represents the top of a another scarp and row 4 represents the bottom of this other scarp, and so on. I want to calcualte the slope and height for each scarp. Therefore, I need to calculate the change in x and the change in y for each set of 2 rows representing the top and bottom of each scarp. I can't figure out how. Perhaps I need a loop?

An example of the data is as follows:

x (distance) y (Depth)

3704.43613041155 -1705.01061571125

3839.12346338856 -1751.88959660297

3973.81079636558 -1748.49256900212

4063.60235168359 -1762.76008492569

4211.11704970604 -1738.98089171975

4390.70016034206 -1787.89808917197

4814.00320684126 -1749.17197452229

4852.48530197755 -1766.15711252654

5570.81774452165 -1684.62845010616

5788.88295029396 -1742.37791932059

6526.45644040620 -1662.88747346072

6558.52485301978 -1683.26963906582

Many thanks in advance

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Answer 1

Ameer Hamza 2020-9-16

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/594652-calculations-on-every-2nd-row-in-a-matrix-in-sets-of-2-rows#answer_495442

在 MATLAB Online 中打开

data.txt

Something like this

f = fopen('data.txt');
data = textscan(f, '%f %f', 'HeaderLines', 1);
fclose(f);
data = [data{:}];
data_part = mat2cell(data, 2*ones(size(data,1)/2,1), 2);
data_diff = cellfun(@(x) diff(x), data_part, 'uni', 0);
slopes = cellfun(@(x) x(2)/x(1), data_diff);
heights = cellfun(@(x) x(2), data_diff);