Please how can I edit/expand data of a text file in Matlab?

I have a text file with two columns (x1,x2) I do need to expand the data according to the following equations:

x = (x1 + x2)/2 + ((x1-x2)/2)*cos(2Ө) , Ө = -30 :30

y = (x1 + x2)/2 - ((x1-x2)/2)*cos(2Ө) , Ө = -30 :30

xy =  ((x1-x2)/2)*sin(2Ө) , Ө = -30 :30

The result would be a new text file has three expanded columns (x,y,xy).

Thanks

[Walter Roberson]

Are the -30 and +30 intended to be degrees? Is it correct that you need integer degrees from -30 to +30 ? That would seem to be 61 x and y and xy outputs for each input x1 and x2: how do you want that arranged in the output file?

[ND]

Yes, it is in degrees. The output would be a text file with three columns arranged as [ x, y, xy ]. So the new file has only the new data.

[Walter Roberson]

You have a text file with two rows, with x1 and x2 columns. Let the first row of the file be designated as x1_1 and x2_1, and the second row of the file be designated as x1_2 and x2_2, and likewise use _1 to refer to row 1 of the file and _2 to refer to row 2 of the file. Let theta = -30 be represented by tm30 and theta = -29 be represented by tm29 .

Then,

x_tm30_1 = (x1_1 + x2_1)/2 + ((x1_1-x2_1)/2)*cosd(2*(-30))
y_tm30_1 = (x1_1 + x2_1)/2 - ((x1_1-x2_1)/2)*cosd(2*(-30))
xy_tm30_1 = ((x1_1-x2_1)/2)*sind(2*(-30))
x_tm29_1 = (x1_1 + x2_1)/2 + ((x1_1-x2_1)/2)*cosd(2*(-29))
y_tm29_1 = (x1_1 + x2_1)/2 - ((x1_1-x2_1)/2)*cosd(2*(-29))
xy_tm29_1 = ((x1_1-x2_1)/2)*sind(2*(-29))

x_tm30_2 = (x1_2 + x2_2)/2 + ((x1_2-x2_2)/2)*cosd(2*(-30))
y_tm30_2 = (x1_2 + x2_2)/2 - ((x1_2-x2_2)/2)*cosd(2*(-30))
xy_tm30_2 = ((x1_2-x2_2)/2)*sind(2*(-30))
x_tm29_2 = (x1_2 + x2_2)/2 + ((x1_2-x2_2)/2)*cosd(2*(-29))
y_tm29_2 = (x1_2 + x2_2)/2 - ((x1_2-x2_2)/2)*cosd(2*(-29))
xy_tm29_2 = ((x1_2-x2_2)/2)*sind(2*(-29))

Now, what should be the output order?

x_tm30_1 y_tm30_1 xy_tm30_1
x_tm29_1 y_tm29_1 xy_tm29_1
...
x_tm30_2 y_tm30_2 xy_tm30_2
x_tm29_2 y_tm29_2 xy_tm29_2
...

or

x_tm30_1 y_tm30_1 xy_tm30_1
x_tm30_2 y_tm30_2 xy_tm30_2
...
x_tm29_1 y_tm29_1 xy_tm29_1
x_tm29_2 y_tm29_2 xy_tm29_2
...

?

That is, should it be all of the degrees for the first input row, then all of the degrees for the second input row? Or should it be all of the rows with the first degree value, then all of the rows with the second degree value?

[Walter Roberson]

I think you might have missed my question, as you happened to be editing your response at the same time.

[ND]

Sorry, I meant something different. I have text file with two columns one for x1 and second for x2 with many rows as the attached file. I need to calculate the values according to the above equations and write their output in a new file. I think I need to use for loop for (Ө) from -30 to 30 for each value of x1 and x2. Note that the original and output text files do not have any labels just numbers Many thanks for all help.

[Walter Roberson]

Do you want 61 rows of results for the first row of the file, and the 61 rows of results for the second row of the file, and so on?

Or do you want the results for the entire input file for angle -30, and then the results for the entire input file for angle -29, and so on?

Answer 1

[Walter Roberson]

x1x2 = load('p.txt');
ang = -30:30;
nang = length(ang);
X1 = repmat(x1x2(:,1), 1, nang);
X2 = repmat(x1x2(:,2), 1, nang);
ANG = repmat(ang, size(x1x2,1), 1);

X = (X1 + X2)/2 + ((X1 - X2)/2) .* cosd(2*ANG);
Y = (X1 + X2)/2 - ((X1 - X2)/2) .* cosd(2*ANG);
XY = ((X1 - X2)/2) *. sind(2 * ANG);

x = X(:);
y = Y(:);
xy = XY(:);

xyxy = [x, y, xy];

dlmwrite('output.txt', xyxy, ' ');   %space as delimiter

[ND]

Many thanks Walter for your help. Please it is possible to use for loop or you think this better?