Getting an error when plotting a graph

maxW = k * (kv * V)^3 * D^4 * P

I want to plot a graph with P on the y axis and D on the x axis. with x going from 0 to 20 at 0.01 intervals. Can i please know how to do it as the plot function doesnt allow me to do this. I tried this

%Battery
S = 3;
mAH = 4000;
AH = mAH/1000;
C = 40;
V = 11.1;

%motor
kv = 920;

%propellor
k = 5.3 * 10^(-15);

%equations
I = C * AH;
maxW = V * I;

D = (0:0.01:20);
maxW = k * (kv * V)^3 * D^4 * P;
plot(D,P), axis equal;

But it gives an error as;

Error using  ^ 
Inputs must be a scalar and a square matrix.
To compute elementwise POWER, use POWER (.^) instead.

Error in quodtest (line 19)
maxW = k * (kv * V)^3 * D^4 * P;

19  maxW = k * (kv * V)^3 * D^4 * P;

Answer 1

[KSSV]

Replace

maxW = k * (kv * V)^3 * D^4 * P;

with

maxW = k * (kv * V).^3 * D.^4 * P;

[Yemal Bandara]

Thanks for your help. But now i got this.

Undefined function or variable 'P'.

Error in quodtest (line 19)
maxW = k * (kv * V).^3 * D.^4 * P;

19  maxW = k * (kv * V).^3 * D.^4 * P;

i tried declaring P = 0; and plotting the graph, but then i dont get a graph, its a blank white screen.

[KSSV]

You mut know your formulation. If P is a scalar...use only

plot(maxW)

[Steven Lord]

"i tried declaring P = 0; and plotting the graph, but then i dont get a graph, its a blank white screen."

No, you receive a graph. But look at what you're plotting. You're multiplying P by a bunch of other stuff. When P is 0, you're computing 0 times something. What is 0 times just about anything?

[Yemal Bandara]

ohhh.. right right.. i think i might have got it now.. thanks a lot :D