Creating a function with endless errors

function [A2, V_inj, N, A2_tot] = OrfG(mdot, x)
%function
global d
global rho
global k
global deltap
A2 = pi*(d^2/4);
V_inj = sqrt((2*deltap)/(k*rho));
n_temp = mdot /(rho*V_inj*A2);
if x == 0
y = 0;
else
y = 1;
end
N = ceil(n_temp) + y;
A2_tot = N*A2;
end
Then I run
[q, w, r, t] = OrfG(1.53, 0)
I see
>> OrfG(1.53, 0)
Error using /
Matrix dimensions must agree.
Error in OrfG (line 18)
n_temp = mdot /(rho*V_inj*A2);
if I change the code to
n_temp = mdot ./(rho*V_inj)*A2);
and run the same code it shows me a bunch of empty matrices.

回答(2 个)

YOu have to define the global variables...
global d
global rho
global k
global deltap
As you have not defined them,, they will be taken as empty i.e [].
Don't use global variables it's a bad practise , learn to parameterize functions.
See Parameterize function to better understand
d = somevalue;
rho= somevalue;
k= somevalue;
deltap= somevalue;
[A2, V_inj, N, A2_tot] = OrfG(mdot, x,d,rho,k,deltap) % function call just paramterize
function [A2, V_inj, N, A2_tot] = OrfG(mdot, x,d,rho,k,deltap)
%function
A2 = pi*(d^2/4);
V_inj = sqrt((2*deltap)/(k*rho));
n_temp = mdot /(rho*V_inj*A2);
if x == 0
y = 0;
else
y = 1;
end
N = ceil(n_temp) + y;
A2_tot = N*A2;
end

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