How to add equation to function

I need to add my equation (60+(2.13*(t^2))-(0.0013*(t^4))+(0.000034*(t^4.751))) to a function but I cant figure it out. What I've tried just comes out as an error. Please help.

k=1;
for t = 0:2:100;
    h(k) = (60+(2.13*(t^2))-(0.0013*(t^4))+(0.000034*(t^4.751)));
    k = k+1;
    if h>=0
       disp(h);      
    end 
end

This is what I tried but it doesnt work.

k=1;
for t = 0:2:100;
    h(k) = rocket(t)
    k = k+1;
    if h>=0
       disp(h);      
    end 
end

function h(k) = rocket(t)
    h(k) = (60+(2.13*(t^2))-(0.0013*(t^4))+(0.000034*(t^4.751)));
end

Answer 1

[madhan ravi]

Note: the following can be done trivially without a loop by vectorisation.

t = 0:2:100;
h=zeros(size(t));
for k=1:numel(t);
    h(k) = rocket(t(k))
    if h(k)>=0
       disp(h(k));      
    end 
end

function h = rocket(t)
         h = (60+(2.13*(t^2))-(0.0013*(t^4))+(0.000034*(t^4.751)));
end 

Without loop:

t = 0:2:100;
h = rocket(t); 
fprintf('h >= 0:%f\n',h(h>=0))
function h = rocket(t) 
         h = (60+(2.13*(t.^2))-(0.0013*(t.^4))+(0.000034*(t.^4.751)));
end

[Angel Hiram Torres Mota]

Exactly what I was looking for, thanks!

Answer 2

[Star Strider]

Except for your ‘rocket’ function, most of that looks as though it should work.

Leave out the subscript reference when you are declaring your function, and within your function, since ‘k’ is not defined within your function, and is not necessary anyway.

Try this instead:

function h = rocket(t)
    h = (60+(2.13*(t^2))-(0.0013*(t^4))+(0.000034*(t^4.751)));
end

[Angel Hiram Torres Mota]

I wish I could accept all of the 3 answers. Thanks for the help!

[Star Strider]

Again, my pleasure!

How to make a matrix from a for loop

Answer 3

[Adam Danz]

Try using an anonymous function. I also cleaned up the for-loop so it is used properly.

rocketFcn = @(x)(60+(2.13*(x^2))-(0.0013*(x^4))+(0.000034*(x^4.751)));
tm = 0:2:100; 
h = zeros(size(tm)); 
for t = 1:numel(tm)
    h(t) = rocketFcn(tm(t)); 
    if h(t)>=0
        disp(h(t));      
    end 
end

Note that I added ".^" to your rocket function. This allows you to apply vectors to its input so you can avoid the loop.

tm = 0:2:100
h2 = rocketFcn(tm); 

% The two lines above produces the same output as the for-loop!
isequal(h,h2)

[Angel Hiram Torres Mota]

Thank you!

[Adam Danz]

No problem! You can implement the anonymous function I suggested in madhan ravi's solution as well.