Basic Vector Operations

Hello, I am currently familiarizing myself with MATLAB for my research. I was asked to create a program that reads in two vectors from the user and then graph them. I am currently having difficulty correctly performing the the addition and multiplication of these vectors. I am new to this website and MATLAB as a whole. I was hoping someone could assist me in any way.

Thank you, first and foremost for your support. I have spent the last couple of days researching operation techniques and I have come up with the following code for each different function (all of function data may not be included)

for addition:

    a = get(handles.textvector1,'String');

    b = get(handles.textvector2,'String');
    %if length is the same
    if length(a) == length(b)
    %add vectors    
    c = a + b;
    %set text to result
    set(handles.textvectorresult,'String',c);
    %plot result
    plot(c)
    % or display error message
    else
        errordlg('Please enter vectors of same size','Size mismatch error','modal')
    end

      and for multiplication:

a = get(handles.textvector1,'String');

b = get(handles.textvector2,'String');
%if length is the same
if length(a) == length(b)
%add vectors    
c = a .* b;
%set text to result
set(handles.textvectorresult,'String',c);
%plot result
plot(c)
% or display error message
else
    errordlg('Please enter vectors of same size','Size mismatch error','modal')
end

     I end up getting unusually high numbers

Thanks, Prince Njoku

[Oleg Komarov]

http://www.mathworks.com/matlabcentral/answers/6200-tutorial-how-to-ask-a-question-on-answers-and-get-a-fast-answer

Answer 1

[Oleg Komarov]

Matrices and Arrays

• Multiplication (note the dimensions):

 (1:10)   * (21:30).' = scalar  % 1 by 10 times 10 by 1 - inner/dot product
 (1:10).' * (21:30)   = matrix  % 10 by 1 times 1 by 10 - outer product
 (1:10)  .* (21:30)   = vector  % elementwise multiplication

.

• Summation (again note the dimensions)

(1:10)  + 10 or rand(2) + 10 % vector/matrix plus scalar
(1:10)  + (11:20)            % same dim vector addition
rand(2) +  ones(2)           % same dim matrix addition

EDIT

You're retrieving text and doing operations on strings not numbers. To see what I mean try this:

'65' .* '33' 
 65   *  33

To convert strings to numbers a wrapper is:

str2double('65')

or manually for positive numbers:

tmp  = '65' - '0';
nTmp = numel(tmp);
out  = tmp*(10.^(nTmp-1:-1:0)).';

[Prince]

Thanks again. When I convert the strings to a double I recieve one large number. what I am attempting to do is add, subtract, multiply and divide each corresponding element of the two vectors. is there a way to convert each element to it's own integer?

thanks

[Oleg Komarov]

Can you please post an example input string and what you're trying to accomplish.

Does tmp = '65' - '0'; satisfy your request (to separate a string in numeric integers)?

[Prince]

I appreciate your patience.the input is constructed from the user's choice in my code. I prompt the user for a list of a line of numbers with no specific length. then I prompt them for another line with the same length.

Example:

vector 1 = [1 2 3 4 5]

vector 2 = [2 4 5 6 2]

*vectors should be same length in order to operate

could you please explain tmp = '65'-'0' a little further please

thanks

[Prince]

*missing part*

the result should look something like this if you add:

vector result = [3 6 8 10 7]

thanks

[Oleg Komarov]

vector1 + vector2 gives exactly result if they are numeric.

If they are strings

vec1 = '12345';

vec2 = '24562';

Then you need to convert into separate integers.

vec1 -'0' does exactly that.

A string number (ex: '1') is decoded with it's corresponding ASCII numeric value, thus '1' -->double('1') = 49.

'1'-'0' = 49 - 48 = 1 and the result is displayed as double because of the operator "minus".

'123' - '0' operates on all elements of the string array and returns a double vector [1 2 3] and not the scalar 123 directly.

[Prince]

thanks so much!

[westley]

thank you so much man!