Help with executing a least square fitting

Hi I've looked up one of my old .m files and it's been a while since last time I wrote matlab code.

I suspect I'm doing two things wrong here.

1. My "if loops" are not correctly written, I can´t see what im doing wrong here. how should it be written?

2. I can´t use the sign && here. What should i replace it with?

% Executes Least square fitting with matrix method for polynomial
% Entered data: (x,y,deltay,n)
%deltay is the uncertainty in y
%n is the exp for the polynomial highest x-term
%
%Utdata: (A, Deltapar)
%A is the fitting
%Deltapar is the uncertainty in the fitting.

function[A Deltapar] = MKA(x,y,deltay,n)
A = [];
Deltapar = [];
X=[];

%------------------------------------------------------------------------------------------------------------------
% Controls if the matrix format on the indata is in the correct size
if(size(x)(2)~=1)
  x=x';
  endif
if (size(y)(2)~=1)
  y=y';
  endif
if(size(deltay)(2)~=1)
  deltay=deltay';
  endif
  
%------------------------------------------------------------------------------------------------------------------
% controls if the matrices x,y och deltay have the correct format for the execution for the least square fitting.

if(size(x)(2)==1 && size(y)(2) ==1 && size(deltay)(2)==1)

%------------------------------------------------------------------------------------------------------------------
% Executes the least square fitting if the matrices x and y have the same format.
% If not, return a message that says that the matrices x or y is not of the correct length.
  if(length(x)==length(y))
    for i=0:n
      X=[X x.^i];
        end
        for
    sigma=deltay;
    vminus1 = diag(1./sigma.^2);
    A = inv(X' * vminus1 * X) * (X' * vminus1 * y);
    DeltaA = inv(X' * vminus1 * X);
    Deltapar = sqrt(diag(DeltaA));
  else
    disp('x,y  does not have the same length');
  endif
  
%------------------------------------------------------------------------------------------------------------------
% Prints "you have not entered the indata on the correct form."

else 
  disp('You have not entered the data on the correct form');
endif

%------------------------------------------------------------------------------------------------------------------

Thanks in advance.

Friendly Regards.

Answer 1

[Walter Roberson]

size(x)(2) is not valid syntax in MATLAB. () indexing can never be followed directly by () indexing. You should use size(x,2)