Question

let us create a variable for a row vector a = [1, 4, 1, 3, 2, 5, 0] and calculate the mean value of its elements using the Matlab function ‘mean’ and store this value in variable aMean. Fig. 1 gives the Matlab code to do this.

                   a = [1, 4, 1, 3, 2, 5, 0];
                   aMean = mean(a);

Figure 1: Matlab code – row vector and mean of its elements.

Let us now construct a row vector b that contains the indices of elements of a which are larger than the aMean. The code in Fig. 2 performs this by using a ‘for’ loop. Now, add a line into the code to construct a row vector c that contains the values of elements from a which are larger than the mean of a.

              %  With a ‘for’ loop
              j=0;
              for i=1:length(a),

1 1.1

    if a(i)>aMean
        j=j+1;

b(j)=i;

end end

% add line here to construct the row vector c

Figure 2: Matlab code (‘icme Lab1 vectorMan Sept2020 fin.m’) – manipulation of vectors.

Finally, the code in Fig. 3 perform the same as above but using logical operators and ‘find’ function without any use of ‘for’ loop.

The results should be: aM ean = 2.2857, b = (2, 4, 6), c = (4, 3, 5). 1

% Without a ‘for’ loop b_noLoop = find(a > aMean);

Figure 3: Matlab code – manipulation of vectors (logical operators and ‘find’).

Answer 1

code:

output:

raw_code :

a = [1,4,1,3,2,5,0]; %row vector a
aMean = mean(a); %mean of a

%for loop for finding indices
j=0;
for i=1:length(a)
if(a(i)>aMean)
j=j+1;
b(j) = i;
end
end

%to construct the row vector c
c = a(b)
code :

output :

raw_code :

a = [1,4,1,3,2,5,0]; %given data
aMean = mean(a);

b = find(a>aMean); %to find indices without loop
c = a(b)

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