Error:index must be a positive integer or logical.

Anybody can help me whats wrong with my code please. I am constantly getting this error Attempted to access f(1.99); index must be a positive integer or logical.

Error in extreme (line 22) y2=f(x2);

[Shehzad Ahmed]

Then please rectify my code (give it a range of -10,10) function extreme syms x; assume(x,'real') f=input('Enter function:','s'); fun=sym(f); df=diff(fun);

fprintf('\nDerivative of your function is:\n%s\n',char (df)) xmin=input('Enter lower limit of range of function;'); xmax=input('Enter upper limit of range of function;');

if (nargin<4) N=100; end dx=(xmax-xmin)/N; x2=xmin; y2=f(x2); y=[]; for i=1:N x1=x2; y1=y2; x2=xmin+i*dx; y2=f(x2); if (y1*y2<=0) y=fsolve(f,(x2*y1-x1*y2)/(y1-y2)); end end fprintf('\n%f',y)

r=input('\nHow many roots do you see above?'); n=r; disp ('Enter each point indivivually'); for i=1:n fprintf('\nInput point 0%d\n',i) r1=input(':'); y=r1; fprintf('\n Root%d=%f\n',i,y) end

[navya sree]

%back propogation network Program

clear all;

clc;

disp('Back Propogation Network');

v=[0.7 -0.4;-0.2 0.3];

x=[0 1];

t=[1];

w=[0.5;0.1];

t1=0;

wb=-0.3;

vb=[0.4 0.6];

alpha=0.25

e=1;

temp1=0;

while (e<=3)

e

for i=1:2

for j=1:2

temp1=temp1+(v(j,i)*x(j));

end

zin(i)=temp1+vb(i);

temp1=e (-zin(i));

fz(i)=(1/(1+temp1));

z(i)=fz(i);

fdz(i)=fz(i)*(1-fz(i));

temp1=0;

end

for k=1

for j=1:2

temp1=temp1+z(j)*w(j,k);

end

yin(k)=temp1+wb(k);

fy(k)=(1/(1+(e -yin(k))));

y(k)=fy(k);

temp1=0;

end

for k=1

fdy(k)=fy(k)*(1-fy(k));

delk(k)=(t(k)-y(k))*fdy(k);

end

for k=1

for j=1:2

dw(j,k)=alpha*delk(k)*z(j);

end

dwb(k)=alpha*delk(k);

end

for j=1:2

for k=1

delin(j)=delk(k)*w(j,k);

end

delj(j)=delin(j)*fdz(j);

end

for i=1:2

for j=1:2

dv(i,j)=alpha*delj(j)*x(i);

end

dvb(i)=alpha*delj(i);

end

for k=1

for j=1:2

w(j,k)=w(j,k)+dw(j,k);

end

wb(k)=wb(k)+dwb(k);

end

w,wb

for i=1:2

for j=1:2

v(i,j)=v(i,j)+dv(i,j);

end

vb(i)=vb(i)+dvb(i);

end

v,vb

te(e)=e;

e=e+1;

end

i am getting this error please help me out in solving thank you in advance.

Attempted to access e(-0.2); index must be a positive integer or logical.

Error in backpropogation (line 22)

temp1=e (-zin(i));

%Kohonen Self organizing feature maps Program

clear all;

clc;

disp('Kohonen Self organizing feature maps');

disp('The input patterns are');

x=[1 1 0 0; 0 0 0 1; 1 0 0 0;0 0 1 1]

t=1;

alpha(t)=0.6;

e=1;

disp('Since we have 4 input pattern and cluster unit to be formed is 2, the weight matrix is');

w=[0.2 0.8; 0.6 0.4; 0.5 0.7; 0.9 0.3];

disp('the learning rate of this epoch is');

alpha

while(e<=3)

i=1;

j=1;

k=1;

m=1;

disp('Epoch =');

e

while(i<=4)

for j=1:2

temp=0;

for k=1:4

temp= temp + ((w(k,j)-x(i,k) 2);

end

D(j)=temp

end

if(D(1)<D(2))

J=1;

else

J=2;

end

disp('The winning unit is');

J

disp('Weight updation');

for m=1:4

w(m,J)=w(m,J) + (alpha(e) * (x(i,m)-w(m,J)));

end

w

i=i+1;

end

temp=alpha(e);

e=e+1;

alpha(e)=(0.5*temp);

disp('First Epoch completed');

disp('Learning rate updated for second epoch');

alpha(e)

end

i am getting below error

Error: File: kohonenself.m Line: 24 Column: 42

Unexpected MATLAB expression.

Answer 1

[John D'Errico]

You have created (somewhere) a variable f. f is a scalar, a vector or an array.

Where is the 1.99'th element of that array? When did you create that element? The fact is, you cannot stuff something into the 1.99'th place in memory. There is no such place. Yet you have tried to access that memory element.

Since this is clearly impossible, MATLAB returns an error. It told you that your index must be a positive integer, or a logical (boolean) vector. However x2 is apparently the floating point number 1.99. How it got to be that is by your own design, since it was created by your coding.

If you are constantly getting that error, then you need not to try to index variables with real numbers. Perhaps you think of f as a function. It is not. It is a variable, at least as you have created it.

[Shehzad Ahmed]

function extreme syms x; assume(x,'real') f=input('Enter function:','s'); fun=sym(f); df=diff(fun);

fprintf('\nDerivative of your function is:\n%s\n',char (df)) xmin=input('Enter lower limit of range of function;'); xmax=input('Enter upper limit of range of function;');

if (nargin<4) N=100; end dx=(xmax-xmin)/N; x2=xmin; y2=f(x2); y=[]; for i=1:N x1=x2; y1=y2; x2=xmin+i*dx; y2=f(x2); if (y1*y2<=0) y=fsolve(f,(x2*y1-x1*y2)/(y1-y2)); end end fprintf('\n%f',y)

r=input('\nHow many roots do you see above?'); n=r; disp ('Enter each point indivivually'); for i=1:n fprintf('\nInput point 0%d\n',i) r1=input(':'); y=r1; fprintf('\n Root%d=%f\n',i,y) end

Then please rectify my code (give it a range -10,10)

[John D'Errico]

You may THINK of the function as entered as a function. It is NOT so! f is just a string of characters.

Numbers and characters mean NOTHING unless you attribute some meaning to them.

f=input('Enter function:','s')
Enter function:s^2 + 2
f =
s^2 + 2
>> f(1.99)
Subscript indices must either be real positive integers or logicals.

As you can see, it generates the same error that you got.

You can use matlabfunction to convert a symbolic expression (like that in fun) into a function handle, something that one can evaluate.