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functions from a single script M-file and link the parameters’ values together
so that you only need to edit the calling script M-file. To link the values of
parameters to all functions in use, you can use the MATLAB global com-
mand. To see how this works, rewrite the above function M-files as follows:

function I=L1(V)
global R1 R % global statement
Vs=5;
I=(Vs-V)/R1;

function I=L2(V)
global R1 R % global statement
Vs=5;
I=V/R;

The calling script M-file now reads:

global R1 R %global statement
R1=100; %set global resistance values
R=100;
V=0:.01:5; %set the voltage range
I1=L1(V); %evaluate I1
I2=L2(V); %evaluate I2
plot(V,I1,V,I2,'-') %plot the two curves

In-Class Exercise

Pb. 3.6 In the above script M-file, we used arrays and the plot command.
Rewrite this script file such that you make use of the fplot command.

Further Consideration of Figure 3.1
Calculating the circuit values for fixed resistor values is important, but we
can also ask about the behavior of the circuit as we vary the resistor values.
Suppose we keep R = 100Ω and V = 5 V fixed, but vary the value that R can
1 s
take. To this end, an analytic solution would be useful because it would give
us the circuit responses for a range of values of the circuit parameters R , R,
1
V . However, a plot of the lines L and L for different values of R can also pro-
s 1 2
vide a great deal of qualitative information regarding how the simultaneous
solution to L and L changes as the value of R changes.
1 2

© 2001 by CRC Press LLC