use of If else condition

Hi all, I am trying to plot a function in which If else condition is required.

I wrote a following code, May any body correct it...

code:

clear all
clc
format longEng
syms  z1 z2 z
phi=(pi/180)*39;
delta=(pi/180)*26;
gma=18.4;
h=4;
h1=1.91;
h2=0.08;
L=h+h1+h2;
beta=1;
alfa=1;
z1=z-h;
z2=z-h-h1;
Ra1=-1; 
Ra2=-(alfa*(z2/h2))^0.5;
Rp1=3*(beta*(1-(z1/(h1))))^0.5;
Rp2=3*(alfa*(z2/h2))^0.5;

delma1=0.5*(1-Ra1)*delta;
delma2=-0.5*(1-Ra2)*delta;
delmp1=0.5*(Rp1-1)*delta;
delmp2=0.5*(Rp2-1)*delta;

ka1=(2*cos(phi)^2)/(cos(phi)^2*(1+Ra1)+cos(delma1)*(1-Ra1)*(1+sqrt((sin(phi+delma1)*sin(phi))/cos(delma1)))^2);
ka2=(2*cos(phi)^2)/(cos(phi)^2*(1+Ra2)+cos(delma2)*(1-Ra2)*(1+sqrt((sin(phi+delma2)*sin(phi))/cos(delma2)))^2);

kp11=(2*cos(phi)^2)/(cos(phi)^2*(1+Rp1)+cos(delmp1)*(1-Rp1)*(1+sqrt((sin(phi+delmp1)*sin(phi))/cos(delmp1)))^2);
kp12=1+0.5*(Rp1-1)*((cos(phi)^2/(cos(delmp1)*(-sqrt((sin(phi+delmp1)*sin(phi))/cos(delmp1))+1)^2))-1);
if Rp1<1 
    k=kp11;
else
    k=kp12;
end

kp21=(2*cos(phi)^2)/(cos(phi)^2*(1+Rp2)+cos(delmp2)*(1-Rp2)*(1+sqrt((sin(phi+delmp2)*sin(phi))/cos(delmp2)))^2);
kp22=1+0.5*(Rp2-1)*((cos(phi)^2/(cos(delmp2)*(-sqrt((sin(phi+delmp2)*sin(phi))/cos(delmp2))+1)^2))-1);
if Rp2<1 
    k=kp21;
else
    k=kp22;
end

 
pa1=ka1; 
pp1=k;
pp2=k;
pa2=-ka2;

fplot(pa1,[0 h+h1])
hold on
fplot(pp1,[h h+h1])
hold on
fplot(pp2,[h+h1 L])
hold on
fplot(pa2,[h+h1 L])
hold off
grid on

[Geoff Hayes]

Akshay - are Rp1 and Rp2 symbolic expressions? Do you need to convert it to a double (numeric value) before trying to compare either with 1?

Answer 1

[Naman Bhaia]

Hey Akshay,

I have looked at the question and I believe it is similar to a previously answered question, I hope this link helps.

[Akshay Pratap Singh]

Thanks Naman. As I am new to MATLAB, could you please correct it.

Thanks in advace.

[Naman Bhaia]

So I havent looked at what the code is trying to do but to resolve the issue, define the value for 'z' somewhere and then do one of the following for comparing the values:

1. if eval(subs(Rp1))>1, or
2. if double(subs(Rp1))>1

Try and see which option suits you.

[Akshay Pratap Singh]

I tried. It is giving wrong answers. You please check.