how to execute str2num or str2double in matlab?

I am having trouble using commands str2num.

I have a character

t='2'
  'u1'
  'u2 '

I used the command p=str2double(char(t)). Right now if I use str2num, a null array appears in the output whereas using str2double gives NaN in output. While searching about these I learned that these character values are not converted to numbers.

I wanted p to store values [2, 1, 2]. How can I do that? Thanks for reading...

[Walter Roberson]

Is t a char vector that might at different times have '2' or 'u1' or 'u2 ' ? Or is t a cell array of character vectors that has those three character vectors in it? Or is t a single character vector '2 u1 u2 ' ?

In the number portion, is it necessary to recognize negative values? Is it necessary to recognize decimal points and fractions? How about exponential numbers? How about complex values?

[MEENAL SINGHAL]

Thank you for responding. t here is a 3x1 cell array containing 3 characters '2' 'u1' 'u2'. My code is:

function sol=AdomPoly(expression,nth) 
% Coded by H. F. & H. A., Feb, 2011 
Ch=char(expand(expression));
s=strread(Ch, '%s', 'delimiter', '+');

for i=1:length(s)
t=strread(char(s(i)), '%s', 'delimiter', '*()expUlogsinh');
t=strrep(t,'^','*');
if length(t)~=2 
    p=str2double(char(t));
    sumindex=sum(p)-p(1);
else
    sumindex=str2double(char(t));
end
list(i)=sumindex ;
end
A='';
for j=1:length(list)
if nth==list(j) ;
    A=strcat(A,s(j),'+');
end
end
N=length(char(A))-1;
F=strcat ('%',num2str(N),'c%n');
sol=sscanf(char(A),F);
end

Further the expression = (u0+u1+u2)^2; nth=2; where u0, u1, u2 are symbolic variables.

[per isakson]

Hint:

t = { '2' 'u1' 'u2 '};
c = regexp( t, '[\d ]+', 'match' );
p = cellfun( @str2double, c )

outputs

p =
     2     1     2

[MEENAL SINGHAL]

Thanks @per isakson for the hint [and for editing my question :)]. It works individually in command prompt but gives a error saying "set UniformOutput to false" when I run the same with the complete code.

Answer 1

[Stephen23]

Simple, and possibly the most efficient way:

>> t = {'2','u1','u2 '};
>> sscanf([t{:}],'%du')
ans =
   2
   1
   2

[MEENAL SINGHAL]

Thanks Stephen Cobeldick for answering. The problem is solved for

t='2'
  'u1'
  'u2 '

But what if I have

t=  'u0*2 '
    'u1*2 '
    'u2*2 '

Now I want 'p' to store [0*2 1*2 2*2] ,i.e., [0 2 4]. How can I do that?

[Stephen23]

@MEENAL SINGHAL: Perhaps you are asking about how to write a maths parser, which in general is not a trivial task. What operators do you expect to have? For simple multiplication:

>> t = {'u0*2','u1*2','u2*2'};
>> v = sscanf([t{:}],'u%d*%d');
>> v(1:2:end).*v(2:2:end)
ans =
   0
   2
   4