Got an indexing error here. Please recommend an answer.

for i=1:9

      N_matrix(1,i)=N(rem(i,3))*ex(i)/3; %(ERROR HERE)
  end

Attempted to access N(0); index must be a positive integer or logical.

Error in practisee2 (line 227)
    N_matrix(1,i+1)=N(rem(i+1,3))*ex(i+1)/3;

[madhan ravi]

did you see about indexing?

[Walter Roberson]

rem(i,3) for integer i is going to give one of the results 0, 1, or 2. What output are you expecting if the rem gives 0 ?

[Kevin Chng]

for i=1:9
    N_matrix(1,i)=N(rem(i,3))*ex(i)/3;%(ERROR HERE)
end

when i =3, rem(3,3) will return 0, N(0) cause you error? Why?

N is one of your matrix/variable, index must be a positive integer or logical.

N(1) % No error

N(0) % error because it is not a positive integer

N(0.5) % error because it is not positive integer

N(-1) % error because it is not positive integer

[KSSV]

N(rem(i,3))

for i = 3, rem(i,3) will be zero.....and obviously you know that MATLAB do not have zero indexing. So the error. :)

[Virajan Verma]

I am expecting 0 at rem(3,3), but N(0) is not accessable as shown above.

[madhan ravi]

upload your data N and let us know what you want N(rem(i,3)) with this syntax?

[KSSV]

@ Virajan Verma you asked question yesterday that you are unable to access N(i) from i = 0:8, so we said MATLAB will not take indexing zero. It shall be positive non-zero integers. YOu accepted the answer. What have you learned from the question? You learned that N(0) is not right, it throws error. What is present question? It is same as above or not? It is not fair to ask every step a question in forum. I suggested/ adivced you to read basic tutorials of MATLAB which is very easy.

[madhan ravi]

exactly as KSSV says , would you mind uploading the so called mystery N ??

[KSSV]

N is a matrix formed from Shape functions. It is related FEM (Finite Element Method) stuff.

[madhan ravi]

thank you @KSSV

Answer 1

[Walter Roberson]

        N_matrix(1,i)=N(rem(i-1,3)+1)*ex(i)/3; %(ERROR HERE)

[Virajan Verma]

@Walter Will this expression will result in the same output??

[KSSV]

Will this expression will result in the same output ..You try....play with values see the output..make a note..change the values....compare the output...remember you are learning..this is the way to learn.

[Walter Roberson]

"Will this expression will result in the same output??"

No. Your original expression outputs an error message, whereas my proposed expression will execute.