Troubles with plotting two functions in one graph

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N/A
N/A 2014-1-16
评论： N/A 2014-1-16
I am having troubles with the following code:
function polarisatiecurve
P = 100
I = 0:0.0001:200;
U1 = P/I;
U2 = 800*(I+19)^2 - 2*(I+19)^3;
plot(I,U1,'b',I,U2,'r',[0,100,0,600]);
subplot (1,2,1);
xlabel('Stroom (A)')
ylabel('Spanning (V)')
title('Polarisatiecurve')
axis([0 120 0 4000])
grid on
grid on
end
What I want to do is plot two functions in one graph. The terms 'polarisatiecurve, stroom, spanning' are Dutch and mean polarisation curve, current (stroom) and voltage (spanning). What I want is that it plots two functions in the same graph. Both functions depend on the current I (the 'stroom'). However I can't get it to work. It gave me the following error:
Error using / Matrix dimensions must agree.
Error in polarisatiecurve (line 4) U1 = P/I;
That refers to the following line of code:
I tried converting I to a symbolic expression but that didn't work either. Who knows how to fix it?

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Amit
Amit 2014-1-16
编辑：Amit 2014-1-16
Few errors: like U1 = P/I. This is invalid operation as I is a matrix. To do this you use '.' operator. Similarly for ^, you will use .^ instead for the operations for matrixes.
function polarisatiecurve
P = 100;
I = 0:0.0001:200;
U1 = P./I;
U2 = 800*(I+19).^2 - 2*(I+19).^3;
plot(I,U1,'b',I,U2,'r'); %,[0,100,0,600]);
%subplot (1,2,1);
xlabel('Stroom (A)')
ylabel('Spanning (V)')
title('Polarisatiecurve')
%axis([0 120 0 4000])
grid on
grid on
end
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Amit
Amit 2014-1-16
编辑：Amit 2014-1-16
The problem is that they intersect between 0 and 0.001 and 0 to 200 is a much bigger range for this. Try this
function polarisatiecurve
P = 100;
I = 0:0.000001:0.001;
U1 = P./I;
U2 = 800*(I+19).^2 - 2*(I+19).^3;
plot(I,U1,'b',I,U2,'r'); %,[0,100,0,600]);
%subplot (1,2,1);
xlabel('Stroom (A)')
ylabel('Spanning (V)')
title('Polarisatiecurve')
axis([0 0.001 0 0.5e6])
grid on
grid on
end
N/A
N/A 2014-1-16
Never mind, I needed to add an axis options after the plotting function. Thank you so much for helping me!

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