Path: news.mathworks.com!not-for-mail From: <HIDDEN> Newsgroups: comp.soft-sys.matlab Subject: Please Help! Date: Tue, 30 Nov 2010 03:24:05 +0000 (UTC) Organization: University of Colorado Denver Lines: 58 Message-ID: <id1qol$t4u$1@fred.mathworks.com> Reply-To: <HIDDEN> NNTP-Posting-Host: webapp-02-blr.mathworks.com Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Trace: fred.mathworks.com 1291087445 29854 172.30.248.37 (30 Nov 2010 03:24:05 GMT) X-Complaints-To: news@mathworks.com NNTP-Posting-Date: Tue, 30 Nov 2010 03:24:05 +0000 (UTC) X-Newsreader: MATLAB Central Newsreader 2492023 Xref: news.mathworks.com comp.soft-sys.matlab:691067 Hello, I'm not very adept at using MatLab and have been struggling with this problem for hours now. I have two equations I am trying to solve for I and V (Current and Voltage): I = Il-Io*(exp((V+I*Rs)/a)-1) V = (Mp*I*Rl)/Ms I have tried to set up a while loop and graphically solve the equations, however, I can't get past the same error: ??? Undefined function or method 'intercept' for input arguments of type 'double'. Error in ==> Pleasework at 21 ind_Inew=intercept(I,eq1,eq2); Here is my code that I'm using: %Enter the given variables Mp=4; Ms=2; Rs=0.533; a=1.005; Il=4.543; Io=2.353*10^-9; Rl=6; %Solve for V and I V_start=10; %Initial guess for V change=1; V=V_start; while change>0.001 %Graphically solve the first equation I=0.01:0.0001:10; eq1=Il-Io*(exp((V+I*Rs)/a)-1); eq2=I; ind_I=intercept(I,eq1,eq2); I=I(ind_I); %Graphically solve the second equation V=2:0.0001:40; eq1=(Mp*I*Rl)/Ms; eq2=V; ind_V=intercept(V,eq2,eq1); V=V(ind_V); change=abs(V-V_start); V_start=V; end V I Any help would be much appreciated. I have been struggling on this problem for awhile now. Thanks. Kevin