error using horzcat function

Very simple code of adding two matrices horizontally retyrns an error using horzcat, dimensions of arrays being concatenated are not consistent. the error is on line (theta = [theta(:,1:6),zeros(length(theta),1)];).

the excel file has a matrix of 4x6, which i check with size theta even.

the code is:

clear all

clc

% Input:

tmp = importdata ('exp.xlsx');

theta = tmp.data;

theta = [theta(:,1:6),zeros(length(theta),1)];

% Calcu

theta (:,7) = theta (:,2).*theta(:,3);

%output

file_name = 'total.txt';

fid = fopen(file_name,'w');

fprintf(fid,'This file is written by matlab code.\n\n');

fprintf(fid,'This code will calculate the total.\n\n');

for i = 1:length(theta)

fprintf(fid,'The total of %d with age %f and exp %f is %f.\n',theta(i,1),theta(i,2),theta(i,3),theta(i,4));

end

fprintf(fid,'\nENDFILE');

fclose (fid);

Answer 1

[VBBV]

theta = [theta(:,1:6),zeros(size(theta,1),1)];

[VBBV]

Preallocate the matrix theta with correct number of zeros

[rida]

THANKS, ERROR RESOLVED. what exactly happened here? it worked when i only had 3 columns

[Steven Lord]

The length function on a non-empty array returns the size in the longest dimension of your array. That's not necessarily the number of rows.

A = ones(3, 6);
length(A)

ans = 6

Calling size with 1 as the dimension input will give you the number of rows in the array.

size(A, 1)

ans = 3

[rida]

thanks, this was very helpful. much thanks

Answer 2

[Satwik]

You can make the following change if your goal is to concatenate.

tmp = zeros(4,6);
theta = tmp;
theta = [theta(:,1:6),zeros(size(theta,1),1)]

theta = 4×7

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0