How to write a specific number via a loop

I have a code that

1)reads two files

2)calculates distances between points of file1 and point of file 2

3) writes an output with the distnces less than 2km.

The problem is that I would like to add to the output file one extra column that concludes specific number of each row

my code is

data=readcell('file1.txt')
lat1=cell2mat(data(4:end,2))
lon1=cell2mat(data(4:end,3))
value=cell2mat(data(4:end,5))

filename1= 'file2.txt' %arxeio me makroseismika

[d1,tex]= importdata(filename1);

lat2=d1.data(:,2);
lon2=d1.data(:,1);
c=d1.data(:,4);

for z=1:numel(stname)
  distances = (deg2km(distance(lat1(z),lon1(z),lat2,lon2)));% Compute distances
  withinkm = distances <= 2; % Find row indexes where the distance is less than 2 km.

  % Extract only those close points from the set of all points.
  closePointskm = [lat2(withinkm), lon2(withinkm), c(withinkm), distances(withinkm), value(z:numel(withinkm))]

  writematrix()
end

The problem is in the line 23.

command window shows me:

Could you please help me?

Answer 1

[dpb]

Other than there aren't 23 lines in the code shown :), the problem is actually in the line

distances = (deg2km(distance(lat1(z),lon1(z),lat2,lon2)));% Compute distances

because you save only the current value you just computed each time through the loop so you don't have but the last value at the end. Then, the same problem occurs with the next line.

Something like

...
distances=zeros(numel(stname),1);       % preallocate the output array
for z=1:numel(stname)
  distances(z)=deg2km(distance(lat1(z),lon1(z),lat2,lon2));
end
withinkm = distances <= 2; % Find row indexes where the distance is less than 2 km.
% Extract only those close points from the set of all points.
closePointskm = [lat2(withinkm), lon2(withinkm), c(withinkm), distances(withinkm), find(withinkm)];
...

This writes the row in the array for which the respective values was found/saved.

You'll then also need to fix up the syntax for the call to writematrix

[Ivan Mich]

Sorry but it is no use. Command window shows me

Error using horzcat

Dimensions of arrays being concatenated are not consistent.

Error in code(line 23)

closePointskm = [lat(withinkm), lon(withinkm), c(withinkm), distances(withinkm), value(z)]

I would like to have in column named valus the value that corresoponts to the line of file 1. I mean something like the putput attached in photo

could you please help me?

[dpb]

That's not the code I wrote that errors -- what I wrote does what you asked for.

[Ivan Mich]

ok. could you please help me to modify my code in order to create the 5th column of the output as I want to be?

[dpb]

I did -- what's wrong with using the solution provided? Your code is incorrect in that it uses the loop index variable in building an output vector inside the loop.

Depending upon just what the definiton of the distance is inside the function, it's quite possible you could use one of the MATLAB builtin pdist functions or straight math operations to return the result.

Almost certainly you could rewrite that function to be vectorized and thereby do without the outer loop entirely....but you didn't divulge that piece of information so that we know.

[Ivan Mich]

The problem is that Output contain different values in th 5th column, and not the same value (see photo)

for example , each line of file1.txt has one value it the 5th column fro each row.

I would like to put in all rows of the output file the same number of value that corresponts to each row (eg. see next photo)

could you please help me?

[Ivan Mich]

I am using this command

closePointskm = [lat(withinkm), lon(withinkm), IMM(withinkm), distances(withinkm), value(z)]

but command windows shows me

Index in position 2 exceeds array bounds (must not exceed 1).

Error in code (line 23)

because one has more than one lines in 5th column. The problem is that I want to "repeat" the same number for all tha output files, no matter how many lines (rows) are included in output file.

Could anyone please help me?

[dpb]

"I want to "repeat" the same number for all tha output files"

That's the first time you've said that; it appeared you were looking to append the location in the file at which the distance search was found to be true from the rest of the code.

For the above, if you know what value "value" is to be (there's no hint regarding that in the above code other than it is an array the same size as the rest)

If you know which particular index into the array you're looking for, repmat() will likely be of interest. Otherwise, if it is the values from the array, it would seem the same logical addressing vector would be the logical (so to speak :) ) thing to use to pull the array values corresponding to everything else.

Answer 2

[Oliveira Pereira]

I worked on the old principle

Getting the sum using a for loop implies that you should:

Create an array of numbers, in the example int values.

Create a for statement, with an int variable from 0 up to the length of the array, incremented by one each time in the loop.

In the for statement add each of the array's elements to an int sum.