How to add values for a variable in a loop?

     clc
  clear all
  disp('Finding Stiffness, Displacement & Reactions of a 2nd Order Bar Element ')
  disp('....INPUTS....')

L=60;
E=1000;
Area=10;
Ne=1;%#OF ELEMENTS
o=[];%o=end condition when free & 1=when fixed
%Ne=input('Number of elements=') 
%Le=input('Total Length of bar=')
%E=input('Elastic Modulus=')
%Area=input('Area=')
disp('APPLYING EXTERNAL Boundry Conditions')
n1=1
nn=o
%n1=input('1st Node=')
%nn=input('end Node=') 
%BCs=[N1,Nn]%end conditions,1ST AND LAST NODES ARE FIXED
 % generation equal spaced coordinates

C=E*Area;

%Shape Functions

co=linspace(0,L,Ne+2)%Dividing Element into  Equal SEGMENTS
% n: number of nodes
n=size(co,2)
%Excitation vector
KG=zeros(n,n);%global stiffness matrix(rows,columns)
FG=zeros(n,1);%Global Forces(rows,columns)
        disp('.......ASSEMBLYING  GLOBAL STIFFNESS MATRIX........')

%ii=1:Ne+1
%en2(:,1)=ii
%en2(:,2)=ii+1
%en2(:,3)=ii+2

en2=[1 2 3;3 4 5;5 6 7;7 8 9;9 10 11]
for e=1:Ne+1
% eDof: element degrees of freedom (Dof)
eDof=en2(e,:)%when e=1 it will display 1st row of eDof
%Le=Length/Ne;  %LENGTH OF EACH ELEMENT
Le=co(eDof(2))-co(eDof(1))
syms x
N1=((co(eDof(2)) -(x))*(co(eDof(3)) -(x)))/((co(eDof(2))-co(eDof(1)))*(co(eDof(3))-co(eDof(1))))
N2=((co(eDof(1)) -(x))*(co(eDof(3)) -(x)))/((co(eDof(1))-co(eDof(2)))*(co(eDof(3))-co(eDof(2))))
N3=((co(eDof(1)) -(x))*(co(eDof(2)) -(x)))/((co(eDof(1))-co(eDof(3)))*(co(eDof(2))-co(eDof(3))))
shape(:,1)=N1
shape(:,2)=N2
shape(:,3)=N3
B=diff(shape)
BT=B.'
b=BT*B
x=0.5774 % kindly Help me to put value of x in b 
b=BT*B
Ke=b*C*Le
 KG(eDof,eDof)=KG(eDof,eDof)+ Ke 
 Fe=ff*Le/2*[1;1]
 FG(eDof)=FG(eDof)+Fe 
end
%Ke=C*[1,-1;-1,1]
disp('APPLYING EXTERNAL FORCE')
%fn=input('External Force at node=')
fn=n
%f=input('External Force value=')
f=10
FG(fn)=FG(fn)+f %Force at a perticular node  
disp('Global Stiffness Matrix')
KG
disp('Load Matrix')
FG
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%Boundry Conditions
if  n1==1 & isempty(nn);%1=fixed & 0=free
    c=2
    d=n
    BCs=[1]
    disp('Loop 1')
elseif isempty(n1) &  nn==1;
     c=1
     d=n-1
     BCs=[n]
      disp('Loop 2')
else  n1==1 & nn==1;
     c=2
     d=n-1
     BCs=[1,n]
     disp('Loop 3')
end
MatA=KG(BCs,c:d)%auxaliry equation for initial and final conditions selecting 1st row 2nd & 3rd col.
MatB=FG(BCs)%Aux. Right Hand side i-e force vector

%disp('Matrix witout BC rows')
KG(BCs,:)=[]; %Matrix witout BC rows  
%disp('Matrix witout BC columns')
KG(:,BCs)=[];%Matrix witout BC columns
%disp('Matrix without BC rows from force matrix')
FG(BCs)=[]; %Matrix without BC rows from force matrix
disp(' Stiffness & Force Matrix for displacement cal. ')
KG
FG
disp('Displacements')
Displacements=inv(KG)*FG
disp('Reactions')
Reactions=MatA*Displacements-MatB

[James Tursa]

Which is line 57? What would you like as a result?

[Adi]

I want the the code to use values of x and solve b but as you can see it is not using value of x rather variable is still present.

It is showing following error:

b =

[ (x/900 - 1/20)^2, -(x/450 - 1/15)*(x/900 - 1/20), (x/900 - 1/20)*(x/900 - 1/60)] [ -(x/450 - 1/15)*(x/900 - 1/20), (x/450 - 1/15)^2, -(x/450 - 1/15)*(x/900 - 1/60)] [ (x/900 - 1/20)*(x/900 - 1/60), -(x/450 - 1/15)*(x/900 - 1/60), (x/900 - 1/60)^2]

Ke =

[ 300000*(x/900 - 1/20)^2, -300000*(x/450 - 1/15)*(x/900 - 1/20), 300000*(x/900 - 1/20)*(x/900 - 1/60)] [ -300000*(x/450 - 1/15)*(x/900 - 1/20), 300000*(x/450 - 1/15)^2, -300000*(x/450 - 1/15)*(x/900 - 1/60)] [ 300000*(x/900 - 1/20)*(x/900 - 1/60), -300000*(x/450 - 1/15)*(x/900 - 1/60), 300000*(x/900 - 1/60)^2]

The following error occurred converting from sym to double: Error using symengine (line 59) DOUBLE cannot convert the input expression into a double array. If the input expression contains a symbolic variable, use VPA.

Error in FEM (line 60) KG(eDof,eDof)=KG(eDof,eDof)+ Ke

[Adi]

sorry about line 57! its the line where i have given x=0.5774

[Adi]

Alternatively I can use Integration to solve for element Stiffness Matrix "ke" but again I dont know how to Integrate Matrix.