Index exceeds number of array elements

here's my code - when i run it i get "index exceeds number of array elements" at line 7 but there's 7 elements in temp so im not sure why im getting the error?

altitude = 0.0; 11.0; 20.0; 32.0; 47.0; 51.0; 71.0;

lapse_rate = -6.5; 0.0; 1.0; 2.8; 0.0; -2.8; -2.0;

temp = 288; 0; 0; 0; 0; 0; 0;

% t(n+1) = t(n) + altitude*lapse rate

for i = 1:7

j = i+1;

temp(j) = temp(i)+altitude(j)*lapse_rate(j);

end

temp

[Torsten]

if i = 7, j is 8. The arrays you defined have only 7 elements. So the index exceeds the number of array elements for j=8 (8 is greater than 7).

Answer 1

[Voss]

Actually those variables are scalars (only one element each):

% after "altitude =   0.0;" the rest of the line has no effect:
altitude =   0.0; 11.0; 20.0; 32.0; 47.0; 51.0; 71.0;
% similarly here:
lapse_rate = -6.5; 0.0; 1.0; 2.8; 0.0; -2.8; -2.0;
% and here:
temp = 288; 0; 0; 0; 0; 0; 0;
whos

  Name            Size            Bytes  Class     Attributes

  altitude        1x1                 8  double              
  ans             1x1                 8  double              
  lapse_rate      1x1                 8  double              
  temp            1x1                 8  double              

Put brackets around the expressions to make the variables have 7 elements each:

altitude =   [0.0; 11.0; 20.0; 32.0; 47.0; 51.0; 71.0];
lapse_rate = [-6.5; 0.0; 1.0; 2.8; 0.0; -2.8; -2.0];
temp = [288; 0; 0; 0; 0; 0; 0];
whos

  Name            Size            Bytes  Class     Attributes

  altitude        7x1                56  double              
  ans             1x1                 8  double              
  lapse_rate      7x1                56  double              
  temp            7x1                56  double              

Now you will still get the error because you're indexing altitude and lapse_rate with j, which is one more than i, so j goes to 8 (the error is not because of indexing temp):

% t(n+1) = t(n) + altitude*lapse rate
for i = 1:7
    j = i+1;
    % when i is 7, j is 8
    % trying to get altitude(8) and lapse_rate(8) gives you the error:
    temp(j) = temp(i)+altitude(j)*lapse_rate(j);
end

Index exceeds the number of array elements. Index must not exceed 7.

temp

Maybe you mean to do this:

% t(n+1) = t(n) + altitude*lapse rate
for i = 1:7
    j = i+1;
    temp(j) = temp(i)+altitude(i)*lapse_rate(i);
end