im finding error in line 18

close all;
clc
Pav=30;              %power of laser%
M=1670;              %melting point of SS316%
De=8238*10^(-18);    %Density of SS316%
cp=468;              %specific heat capaityof material%
dx=2;                %X direction increment%
dz=0.4;              %y direction increment%
K=13.4*10^(-6) ;     %thermal conductivity%
lm=300*10^3;         %Latent heat of melting%
dt=10;               %time increment from equation%
Du=75;               %total laser pulse duartion%
f=148;               %laser pulse frequemcy in kilo heartz%
D=K/De*cp;           %dissusivity%
Ro=20;               %laser spot radius%
for j=0:2:400        %x axis loop%
    for k=0:0.4:80   %z axis loop%
        T(0,j,k)=298;    %initial condition%       line 17
    end
end
for i=1:10:75        %time loop%
    T(1:10:75,0,0:0.4:80)=298;  %boundry condition%
    T(1:10:75,400,0:0.4:80)=298;
    T(1:10:75,0,0)=298;
    S=T(i,j,k);
    if T(i,j,k)==M
        T(i,j,k)=T(i-1,j,k)-(lm/cp);    %temp check Melting point%
    else
        for j=1:0.2:400                 %x axis loop%
            for k=1:0.4:8               %y axis loop%
                T(i+1,j,k)=T(i,j,k)*(1-2*dt*D/dx^2-2*dt*d/dz^2)+...
                    dt*D*((dz^2)*(T(i,j+1,k)+T(i,j-1,k))+(dx^2)*(T(i,j,k+1)+T(i,j,k-1)))/(dx^2)*(dz^2)+...
                    (dt*D)/K *AL *(Pav/(f*Du*pi*Ro^2))*exp*(-2*(j/Ro)^2-2*(i/Du)^2-(AL * K));
            end
        end
    end
end

plot3(T(i,80/2,0:0.4:80),i,k)  ;

im finding error in line 17

error

Index in position 1 is invalid. Array indices must be positive integers or logical values.

Error in corsework (line 17)

T(0,j,k)=298; %initial condition%

Answer 1

[KSSV]

Note that the index of array starts from 1 in MATLAB. You have used index as 0, so error.

Also the logic you have used is not correct. This loop:

for j=0:2:400        %x axis loop%
    for k=0:0.4:80   %z axis loop%
        T(0,j,k)=298;    %initial condition%       line 17
    end
end

The above has no logic. Note that.

1. Index should be 1
2. You are skipping the indices, so matrix will create extra zeros at places skipped.
3. Index cannot be a fraction.

Rethink on your code and please read some basics of MATLAB.

Answer 2

[Image Analyst]

Perhaps instead of that loop assigning 298 to everything you simply want

% Get a list of all the j and k we want to iterate over.
allj = 0:2:400;
allk=0:0.4:80;
numj = length(allj)
numk = length(allk)
T = 298 * ones(76, numj, numk);