Enter the val value such that it must contain in x, then only following give some non zero value
i=find(x==val);
Other wise If you enter like as follows
Enter all values in row vector
Enter the values of x=[1 2 3 4]
Enter the values of function at x f(x)=[1 2 4 5]
Enter the value of x at which derivative is to be calculated=6
Now form the next statemnet
i=find(x==val);
Find in x, which equal to 6, actually 6 is not there, hence it return null
>> whos i
Name Size Bytes Class Attributes
i 1x0 0 double
which leads to zero in the equations.
Following gives non zero result, where I have choose val=2, which is part of x vector.
Enter all values in row vector
Enter the values of x=[1 2 3 4]
Enter the values of function at x f(x)=[1 2 4 5]
Enter the value of x at which derivative is to be calculated=2
Following are the Difference Derivatives
FDD CDD BDD
2.0000 1.5000 1.0000
Hope it Helps!
