请坛子里高手帮我看看这个MATLAB程序怎么修改，谢谢！-经管之家官网！

这是程序原文：
%%%%% Matlab program (.m) file that gives solutions to "Problem Set Zero"
%%%%% You should play with this file to learn simple Matlab commands.
%%%%% Use "help" at the command window to figure out what various commands
%%%%% do. Eg, type "help clear" to figure out what the next line does.
clear all
%%%%% QUESTION 1: STEADY STATE
%%%%% Declare parameter values
g = 0.03;
n = 0.01;
s = 0.20;
alpha = 0.33;
delta = 0.04;
parameters = [g;n;s;alpha;delta];
%%%%% Declare some symbols
syms kk gg nn ss aa dd
answer = solve('(1+gg)*(1+nn)*kk-ss*kk^aa-(1-dd)*kk=0',kk);
k_bars = double(subs(answer,{gg,nn,ss,aa,dd},parameters))
% Matlab treats "symbols" differently to "numbers"; the commands above
% declare some symbols then solve the difference equation for its
% steady-state values. I then substitute the vector of parameters into the
% answer to get "numbers" back. Use the Matlab syntax "help syms", "help
% solve" etc etc to investigate this more closely.
% Keep the non-trival (positive) steady-state for future reference

k_bar= max(k_bars);
ky = k_bar^(1-alpha);
mpk = 1+alpha*k_bar^(alpha-1);
display(['Non-trivial steady state = ',num2str(k_bar)])
display(['Capital/output ratio = ',num2str(ky)])
display(['Gross marginal product of capital = ',num2str(mpk)])
%%%%% QUESTION 2: TRANSITION TO STEADY STATE
error = 10;
iter= 1;
k0 = k_bar*exp(-0.5);
% This sets the initial condition while the next command sets up an empty
% vector that we will use to store the sequence of capital stocks.
kt = [];
% The following loop iterates on the difference equation until the error is
% small (less than 10e-6)
while error > 10e-6
if iter == 1
k = k0;
else
k = kt(iter-1);
end

k1 = (s/((1+g)*(1+n)))*k^(alpha) + ((1-delta)/((1+g)*(1+n)))*k;
% The previsious line computes the subsequent capital stock k1 given
% today's capital stock k

error = abs(k1-k_bar);
kt = [kt;k1];
iter= iter+1;

end
T = length(kt);
t = [0;cumsum(ones(T-1,1))];
figure(1)
plot(t,kt,t,k_bar*ones(T,1),'k--')
title('Figure 1: Time path of the capital stock')
xlabel('time, t')
ylabel('capital stock, k(t)')
legend('k(t)',0)
%%%%% Now for the phase diagram (this is a little tricky...)
kmax = 2*k_bar;
ks = linspace(0,kmax,1000);
psis = (s/((1+g)*(1+n)))*ks.^(alpha) + ((1-delta)/((1+g)*(1+n)))*ks;
kt0 = kt(1:T-1);
kt1 = kt(2:T);
figure(2)
if k0 < k_bar
plot(kt0,kt1,'b>-',ks,ks,'k--',ks,psis,'r-')
title('Figure 2: Phase diagram')
else
plot(kt0,kt1,'b<-',ks,ks,'k--',ks,psis,'r-')
title('Figure 2: Phase diagram')
end
xlabel('k(t)')
ylabel('k(t+1)')
legend('k(t+1)','45-degree line','\psi(k(t))',0)
%%%%% PROBLEM 3: GROWTH RATE APPROXIMATIONS
%%%%% The next command produces a 1000-by-1 vector of evenly spaced "zs"
%%%%% between 0 and 1.
zs = linspace(0,1,1000)';
g_approximate = log(1+zs);
g_actuals = zs;
figure(3)
plot(100*zs,100*g_approximate,'k--',100*zs,100*g_actuals)
title('Figure 3: Accuracy of log-differences as aproximate growth rates')
xlabel('growth rate (%)')
legend('log-approximate growth rate','actual growth rate',0)
运行后显示如下错误：
??? Attempt to execute SCRIPT solve as a function.
Error in ==> D:\Matlab\toolbox\symbolic\@sym\solve.m
On line 49==> [varargout{1:max(1,nargout)}] = solve(S{:});
Error in ==> D:\Matlab\work\ps0_solutions.m
On line 25==> answer = solve('(1+gg)*(1+nn)*kk-ss*kk^aa-(1-dd)*kk=0',kk);
谢谢！！！