How can I make a loop the changes for the specified values?

I am trying to set time increment n such that it always corresponds to a 2 degree increment in TH2 based on current omega2. However, I do not believe my loop is set up to evaluate at a 2 degree increment. I do not know what steps to take to make my code run properly.

w2=2*pi;
TH2=0;
t=2
a2=0.5*t;
L2=50;
L3=150;

for n=1:2:length(w2)

TH3(n)=acosd((L2*cosd(TH2))/L3)
d(n)=((L2*sind(TH2(n)))-(L3*sind(TH3(n))))
w3(n)=(L2*w2*sind(TH2(n)))/L3*sind(TH3(n))
d2(n)=(L2*w2*cosd(TH2(n)))-L3*w3*cosd(TH3(n))
a3(n)=((-L3*w3^2*cosd(TH3(n)))+(L2*a2*sind(TH2(n))))+(L2*w2^2*cosd(TH2(n)))/L3*sind(TH3(n))
d3(n)=(L2*a2*cosd(TH2(n)))-(L2*w2^2*sind(TH2(n)))-(L3*a3*cosd(TH3(n)))+(L3*w3^2*sind(TH3(n)))
end

Answer 1

[Star Strider]

The problem is that your ‘w2’ is a scalar of size (1 x 1), so the loop is already satisfied at the first iteration.

This might be closer to what you want to do:

for n=1:2:w2

although ‘n’ will increment in radians, not degrees. To have it increment in degrees, change your loop index to:

for n=1:2:w2*180/pi

or just:

for n=1:2:360

EDIT — Also, ‘TH2’ and ‘TH3’ never change, so all calculations derived from them never change.

[Emily Gobreski]

Thank you for your help! I believe I want my TH2 and TH3 values to change, though. If I want the "2 degree increment in TH2 based on current omega2" will I need a second loop to include the change in TH2 and TH3 values?

[Star Strider]

My pleasure!

I would create a vector for ‘TH2’, then use MATLAB’s vectorisation capabilities, and avoid the loop entirely. See Array vs. Matrix Operations for details.

See if this does what you want:

w2=2*pi;
TH2=0;
t=2;
a2=0.5*t;
L2=50;
L3=150;

TH2 = 0:2:360;

TH3=acosd((L2.*cosd(TH2))./L3);
d=((L2.*sind(TH2))-(L3.*sind(TH3)));
w3=(L2*w2*sind(TH2))./L3.*sind(TH3);
d2=(L2.*w2.*cosd(TH2))-L3.*w3.*cosd(TH3);
a3=((-L3.*w3.^2.*cosd(TH3))+(L2.*a2.*sind(TH2)))+(L2.*w2.^2.*cosd(TH2))./L3.*sind(TH3);
d3=(L2.*a2.*cosd(TH2))-(L2.*w2.^2*sind(TH2))-(L3.*a3.*cosd(TH3))+(L3.*w3.^2.*sind(TH3));

One caution —

This statement:

w3=(L2*w2*sind(TH2))./L3.*sind(TH3);

is equivalent to:

w3=(L2*w2*sind(TH2)).*sind(TH3)./L3;

If you want the two terms in the denominator to be multiplied together before you do the division, you have to enclose the terms in paretheses:

w3=(L2*w2*sind(TH2))./(L3.*sind(TH3));

and for the others as well.

[Emily Gobreski]

works perfectly! Thank you for explaining the error! I appreciate your help!

[Star Strider]

As always, my pleasure!