HELP function y=lagrange (n,x,y) ↑ Error: Function definition not supported in this context. Create functions in code file.

function y=lagrange (n,x,y)
 ↑
Error: Function definition not supported in this context. Create
functions in code file.

this is my code:

function y=lagrange(n,x,y)

      p=size(x,2);

      H=ones(p,size(n,2));

      if (size(x,2)~=size(y,2))

          fprintf(1,'\nERROR…\n x and y must contain equal no. of elements\n');

          y=NaN;

      else

          for i=1:p

              for j=1:p

                  if (i~=j)

                      L(i,:)=L(i,:).*(n-x(j))/(x(i)-x(j));

              end

          end

      end

      y=0;

      for i=1:p

          y=y+y(i)*L(i,:);

      end

end

[Walter Roberson]

You should store the code in a file named lagrange.m

It is not possible to create functions at the command prompt.

In R2016b and later, it is possible to create functions inside a script file, but not in R2016a or earlier. I think the error message was different when you tried in R2016a or earlier.

Answer 1

[madhan ravi]

 %SCRIPT FILE
  x = yourdata
  y = yourdata
  n = your_data
  Y=lagrange(n,x,y) %function calling 

%FUNCTION FILE
function y=lagrange(n,x,y)

      p=size(x,2);
      H=ones(p,size(n,2));
      if (size(x,2)~=size(y,2))
          fprintf(1,'\nERROR…\n x and y must contain equal no. of elements\n');
          y=NaN;
      else
          for i=1:p
              for j=1:p
                  if (i~=j)
                      L(i,:)=L(i,:).*(n-x(j))/(x(i)-x(j));
              end
          end
      end
      y=0;
      for i=1:p
          y=y+y(i)*L(i,:);
      end
  end

[Walter Roberson]

Note: this requires R2016b or later if those are all in the same file.

[madhan ravi]

Thank you sir Walter Edited

[madhan ravi]

@Ramirez did you try the answer?