FOR loop taking every row from a matrix

I am working with the survey data from an Excel file, it has only three columns: [Depth, Inclination, Azimuth]. This data then is used to plot a trajectory in the subsurface.

At the momemnt, I am building a code that slightly modifies the above values of Inclination and Azimuth with simple formulas. As for now, I have a FOR loop with synthetic data of uniformly increasing Depth [1:200] and constant values of Incl & Azim, that, for each incriment in Depth (going deeper) calculates the new values of Incl. & Azimuth. Since the Incl. & Azim. values are constant, it's easy now to calculate with every new value of Depth.

Next step and problem: I have the real data of the above columns, [Depth, Inclination, Azimuth], say [X,Y,Z,] with random survey values (i.e., no uniformly increasing depth anymore. It does go deeper, but with different intervals each time; same type of change for the other two). I have imported the Excel into MATLAB and created the [3x159] matrix. I now want to incorporate the values in my FOR loop, such that it takes every row for the calculations as follows:

1. It takes X1 (Depth1), calculates in some formula the values, e.g. modification = X1+1/3;
2. Then it takes Y1, calculates some different values, e.g. Ynew = Y1 + modification;
3. Lastly, it grabs Z1, calculates another value, e.g. Znew = Z1 + modification;

And so on it repeats the same concept for X2,Y2,Z2 etc. until it reaches the end of the survey data. It will give me in the end the new matrix [X, Ynew, Znew].

Doesn't seem too complicated to tell the code to take every row of the data, but can't get it? Any help would be appreciated. Thanks!

Answer 1

[Shubham Gupta]

Let's call input [3x159] matrix be Xin, and the final output [3x159] matrix be Xout. Here's is the code I would try :

Xout = zeros(size(Xin));  % predefine Xout

for i=1:size(Xin,1)  % edited the dimension ( Thanks for the comments )
    X = Xin(i,1);
    Y = Xin(i,2);
    Z = Xin(i,3);
    modification = X + 1/3;
    Ynew = Y + modification;
    Znew = Z + modification;
    Xout(i,:)=[ X, Ynew, Znew];  % save [X, Ynew, Znew] in i-th row
end

[John Pickles]

The code works. Only I used

for i=1:size (Xin)

Instead of

for i=1:size (Xin,2)

Everything else is fine. Thank you very much! Double-checked with the hand-calculator.

What does the number "2" underline here anyway?

[Stephen23]

For clarity it is better to specify the dimension:

size(Xin,1)

[Jan]

@John Pickles: In for i=1:size (Xin), size replies a vector. This is equivalent to:

for i = 1:[3,159]

Now Matlab uses the first element for the colon operator only, and ignores the 159. It works, but Stephen's suggestion is celar and unique:

for i = 1:size(Xin, 1)