Help in Matlab Laplace Equation -

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i have tried implement laplace equation in matlab code sequence shown below. created laplaceexplicit.m , used function numgrid in same. however, shows error "input variable n undefined". should done? code below-

    function [x,y,t]= laplaceexplicit(n,m,dx,dy)     echo off;     numgrid(n,m);     r = 5.0;     t = r*ones(n+1,m+1); % t(i,j) = 1 includes boundary conditions     x = [0:dx:n*dx];y=[0:dy:m*dy]; % x , y vectors     = 1:n % boundary conditions @ j = m+1 , j = 1     6     t(i,m+1) = t(i,m+1)+ r*x(i)*(1-x(i));     t(i,1) = t(i,1) + r*x(i)*(x(i)-1);     end;     tn = t; % tn = new iteration solution     err = tn-t;     % parameters in solution     beta = dx/dy;     denom = 2*(1+beta^2);     % iterative procedure     epsilon = 1e-5; % tolerance convergence     imax = 1000; % maximum number of iterations allowed     k = 1; % initial index value iteration     % calculation loop     while k<= imax     = 2:n     j = 2:m     tn(i,j)=(t(i-1,j)+t(i+1,j)+beta^2*(t(i,j-1)+t(i,j+1)))/denom;     err(i,j) = abs(tn(i,j)-t(i,j));     end;     end;     t = tn; k = k + 1;     errmax = max(max(err));     if errmax < epsilon     [x,y] = meshgrid(x,y);     figure(2);contour(x,y,t',20);xlabel('x');ylabel('y');     title('laplace equation solution - dirichlet boundary conditions explicit');     figure(3);surfc(x,y,t');xlabel('x');ylabel('y');zlabel('t(x,y)');     title('laplace equation solution - dirichlet boundary conditions explicit');     fprintf('convergence achieved after %i iterations.\n',k);     fprintf('see following figures:\n');     fprintf('==========================\n');     fprintf('figure 1 - sketch of computational grid \n');     fprintf('figure 2 - contour plot of temperature \n');     fprintf('figure 3 - surface plot of temperature \n');     return     end;     end;     fprintf('\n no convergence after %i iterations.',k);

matlab go through standard look-up procedure work out represents. first, local variable? if not, function or script (command)? requires looking in prescribed set of places. simple version is: first in current directory, in directories specified matlab path (in order).

hence, if write square_table.m , save in c:\work\moe\matlab directory needs either current working directory on on matlab path. otherwise error ("undefined function or variable").


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