Date: Feb 3, 2013 11:04 AM
Author: dpb
Subject: Re: Problem using plots and loops
On 2/3/2013 1:06 AM, Ankita wrote:

...

> 1) In the first 2 if loops, I want to make sure that the ratio fits in a

> given limit. Is there any better way of doing that?

You could write things like Nmax=min(InputRatio,Limit) etc., but if it

works as is, that's a nicety and since it's just a single set of values

and is in an user input section the time isn't an issue...I'd let it go

until got other things worked out and develop some more familiarity w/

Matlab and programming in general...

> 2) When I execute

> the program, only the fprintf in 2nd if loop is executed. Why is that?

Would seem to be owing to the values you've selected -- altho it's

possible you've written a set of conditions such that one branch can

never be reached because the tests aren't possible--I didn't have time

at the moment to read it that carefully, sorry...

> 3) For the last for loop, I should be get 4 different curves for 4

> values of N. Instead I get one curve (the curve is actually a set of

> points. Not a continuous line. That too is my problem.)

Compute the points in an array and then plot each line when you have a

set of values for the curve instead of each point as it is calculated.

> %NOSE AND MAIN WHEEL LOAD CALCULATION

...

> B=M_f+N_f;

> if M_f/B<0.20

> if M_f/B>0.1

> Nmax=W*(M_f/B);

> else

> Nmax=W*0.15; %max static load per nose wheel

> fprintf('The M_f/B ratio ...

> end

> end

>

> if M_a/B>0.05

> if M_a/B<0.1

> Nmin=W*(M_f/B);

> else

> Nmin=W*0.08; %min static load per nose wheel

> fprintf('The M_a/B ratio has ...

> end

> end

>

...

> %TOTAL STROKE CALCULATION

> %hold on;

> K=L/W;

figure

V=10:15;

for N=1.5:0.5:3

S=(V.^2/2*9.81+S_t*(1-K-0.47*N))/(0.8*N-1+K);

plot(V,S);

hold on

end

Above computes the S vector for each point in the V vector w/o a loop

then plots it.

You'll probably want to add a color value to the plot since the colors

won't automagically cycle unless S is a column vector. Or, you could

create a 2D array and save the whole thing then plot since the sizes are

quite small...

V=[10:15]';

S=zeros(length(V)),4); % preallocate

i=0;

for N=1.5:0.5:3

i = i+1; % array column index

S(:,i)=(V.^2/2*9.81+S_t*(1-K-0.47*N))/(0.8*N-1+K);

end

plot(V,S);

And, of course, one could look at

doc meshgrid

to do the computation w/o any explicit loops at all...

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