Calculation from user input with blank cells

I am working on a project to analyze simple gear trains and have created a dialogue box for the user to input the number of teeth on each gear. The values are used in an equation to calculate the gear train ratio and I am having trouble figuring out how to calculate the ratio if some cells are left blank due to not having 10 gears.

My code so far:

 prompt = {'Gear 1:','Gear 2:','Gear 3:','Gear 4:','Gear 5:','Gear 6:',...
           'Gear 7:','Gear 8:','Gear 9:','Gear 10:'};
    title = 'Number of teeth per gear';
    answer = inputdlg(prompt,title);
    N1 = str2num(answer{1});
    N2 = str2num(answer{2});

    N10 = str2num(answer{10});
    Mo = (N1*N3*N5*N7*N9)/(N2*N4*N6*N8*N10);

Answer 1

[Andrew Newell]

The answer depends on how you would calculate the ratio Mo for fewer gears. If, say, the user omits Gear 3, do you want to simply leave it out, as in this expression?

Mo = (N1*N5*N7*N9)/(N2*N4*N6*N8*N10);

Supposing you do, you could set a default of 1 for the input:

num_lines = 1;
default = repmat({'1'},1,10);
answer = inputdlg(prompt,title,num_lines,default);

[Brandon Page]

Yes, If the user was to omit a gear then it would just be left out of the expression.

Thanks

[Andrew Newell]

An alternative, if you don't want to see those default 1's in the dialog boxes, is to process the answers like this:

N = ones(size(answer));
for ii=1:length(answer)
  if ~isempty(answer{ii})
      N(ii) = str2num(answer{ii});
  end
end

And then you can calculate your expression:

M0 = prod(N(1:2:end))/prod(N(2:2:end));