How can I fix the if statement issue in my code?

Here is my code. I want P_ABP and P_ACP values to be zero if they are smaller than 0. But I still get negative values when I plot the graph. If statement is bolded.

day = 40;

angle_mu = 8;

lat = 30.43;

Ps = 1000;

elev = 59.9;

time = linspace(0,24,24);

alpha = 360/24*(time-12);

dec = 23.44sind(360(day-80)/365.25);

zen = acosd(sind(dec).*sind(lat)+cosd(dec).*cosd(lat).*cosd(alpha));

tan_azi = atand(sind(alpha)./sind(lat).*cos(alpha)-cosd(lat).*tand(dec));

azi = atand(tan_azi);

for i = 1:length(alpha)

if alpha(i) >=0 && tan_azi(i) >=0

azi(i) = 180 + azi(i);

elseif alpha(i) >=0 && tan_azi(i) <=0

azi(i) = 360 + azi(i);

elseif alpha(i) <=0 && tan_azi(i) >=0

azi(i) = azi(i);

elseif alpha(i) <=0 && tan_azi(i) <=0

azi(i) = 180 + azi(i);

end

end

A = 0.433*2;

surf_aziABP = 0;

surf_aziACP = 0;

P_ABP = 0;

P_ACP = 0;

rotation = linspace(1,8,24);

for a = 1:length(time)

surf_aziABP = 60-angle_mu + (rotation(a).*time);

surf_aziACP = 60+angle_mu + (rotation(a).*time);

for b = 1:length(time)

P_ABP = (Ps.*(cosd(elev).*cosd(zen)+sind(elev).*sind(zen).*cosd(azi- surf_aziABP(b))));

P_ACP = (Ps.*(cosd(elev).*cosd(zen)+sind(elev).*sind(zen).*cosd(azi- surf_aziACP(b))));

end

end

if P_ABP < 0

P_ABP = 0;

elseif P_ACP < 0

P_ACP = 0;

end

Power_Total = P_ABP + P_ACP;

POW = A.*Power_Total;

plot(rotation,POW)

grid on

xlabel('Angular Velocity/Hour')

ylabel('Power (W/m^2')

sumPOW = sum(POW)

trapz(time,POW)

Answer 1

[Star Strider]

Replace the if block with:

P_ABP = max(P_ABP,0);
P_ACP = max(P_ACP,0);

With that, I got no negative values whe I ran your code.

[Feyza Boyun]

Tried, it gives me positive values. I was wondering is max() can be used instead of if statement in this case.

[Star Strider]

I do not understand.

You do not want positive values and you do not want negative values.

What is left, except to set both vectors to 0?

[Feyza Boyun]

I want positive values so thank you, it works. I was just wondering can we replace max() with if statement for cases like these

[Star Strider]

As always, my pleasure!

The if block would have to cycle through each element of the vector in a loop, so it is possible to do so, however the max call (or logical indexing) would be more efficient.

[Feyza Boyun]

Great! thanks a bunch.

[Star Strider]

As always, my pleasure!