how to prevent user from entering non-numeric values?

t = 0:0.0001:0.07;

v0 = input('please Enter the value for v0:');

R = input('please Enter the value for resistance:');

C = input('please Enter the value for capacitacne:');

f = input('please Enter the value for frequency:');

m = length(t);

state = 'on';

for A = 1:m

     vs(A) = v0 * sin(2*pi*f*t(A));

    switch state 

        case 'on'

    vR(A) = vs(A);

    iR = vR(A)/R;

    iC = 2*pi*f*C*v0*cos(2*pi*f*t(A));

    I = iC + iR;

    if I<=0

       state = 'off';

       tA = t(A);

    end

        case 'off'

    vR(A) = v0*sin(2*pi*f*tA)*exp(-(t(A)-tA)/(R * C));

      if vs(A) >= vR(A)

          state = 'on';

      end

    end
end

plot (t,vs,':',t,vR,'k')

thank you...

[Azzi Abdelmalek]

amir, You have two flagged questions because you deleted them. You have to restore them

http://www.mathworks.com/matlabcentral/answers/87257#comment_169190 http://www.mathworks.com/matlabcentral/answers/86858-how-can-i-overcome-this-error

[Jan]

@Amir: I agree with Azzi. When we post a solution, we have to expect that you delete the question again and our work is lost for the community. I recommend not to support such a behavior.

See Answers: Is deleting threads useful

[amir]

okay,i restored them...

[Jan]

Please explain the relation between the title and the code. Do you mean the 4 INPUT commands? Then posting the rest is confusing only.

[amir]

yes,i mean the 4 inputs...this is what i got so far .

[Image Analyst]

I noticed you editied it but didn't get it quite right. See this link : http://www.mathworks.com/matlabcentral/answers/13205-tutorial-how-to-format-your-question-with-markup. Basically you don't need to double space your code. all you need to do is to make sure there's a blank line in front of it, then highlight it and click the {}Code button.

Answer 1

[Image Analyst]

Hints: ischar() and isnumeric().

Answer 2

[Jan]

v0S = input('please Enter the value for v0:', 's');
v0  = sscanf(v0S, '%g', 1);
if isempty(v0)
  error('Invalid value for v0');
end

etc.

Of course you cannot prevent, that the user provides non-numeric values, but you can catch this exception.

[amir]

thanks for help,can you give a brief explanation about what you wrote here...