How can I force MATLAB to arrange inputs into a matrix of specified dimensions?

I am currently teaching my self MATLAB. I made a simple program to practice what I have leaned so far but ran into an issue with the input command. Any time I enter a value with more than two characters MATLAB constructs a matrix with each character in a different column (for example 123 yeilds the matrix [1,2,3]). I'm confued because If I run the input command in the command window this doesn't occur. How can I ensure that the input command yeilds a matrix of the correct size ?

%test is a function which calculates the relativistic energy of a particle
% with specified speed (in units of c) and mass (in kg)
help test;
%constant
C=3e8;
%defining variables
B=input('enter the speed of the particle in units of c','s');
disp (size (B))

[Stephen23]

You are mixing up numeric data with character data:

• when you specify the 's' option with INPUT then you have requested its outout to be returned as a character vector: this means if the user inputs five character, you will get a character vector with length five.
• when you write those five character at the command line then they are evaluated, e.g. into a single numeric value.

These are two totally different things.

B = str2double(input('enter the speed of the particle in units of c','s'))

Answer 1

[Yongjian Feng]

Why do you need to know the size of B? Maybe you want

disp(str2double(B))

[Justin Tuttle]

I just used size(B) to diagnose an "incorect dimensions for matrix multiplication" error later in my program that was a result of the matrix being produced by the input function. The same problem is occuring when defining M as well. here's my full program.

%test is a function which calculates the relativistic energy of a partic
% with specified velocity (in units of c) and mass (in kg)
help test;
%constant
C=3e8;
%defining variables
B=input('enter the speed of the particle in units of c','s');
M=input('enter the mass of the particle in kg',"s");

%evaluating energy, and gamma factor
Y=1./sqrt(1-(B.^2));
E=Y*M*C^2;
disp (E)
%displaying gamma if desired
no=0;
yes=1;
Q=input ('would you like the value of gamma (enter yes or no)',"s");
if Q==1
    disp (Y)
end
%displaying momentum if desired
F=input ('would you like the momentum of the particle (enter yes or no)','s');
if F==1
    P=Y*M*B*C;
    disp (P)
end

[Yongjian Feng]

B is an array of char like '123', not a double 123.

str2double converts the input char array '123' into a double of 123.