Please what did i do wrong here..using interp2

i was given a table of y\x and the given values of the corresponding temperatures, and i was told to find the estimate of the temperature at (1.2,0.7). i did my code but it did not seem to be right when i ran it .here is the code:

y=0.0:0.5:2.0;
x=0.0:0.5:2.5;
T= [0.00 5.00 10.00 15.00 20.00;
    5.00 7.51 10.00 12.51 15.00;
    10.00 10.05 10.00 9.95 10.00;
    15.00 12.70 10.00 7.32 5.00;
    20.00 15.67 10.00 4.33 0.00;
    25.00 20.00 10.00 0.00 -5.00;];

 Tn= interp2(x,y,T,1.2,0.7)

Answer 1

[Image Analyst]

All too common of a beginners mistake. You thought x,y = row,column. It's NOT. In other words, you swapped x and y. Remember the rows = y, not x like you had them, and the columns = x, not y like you had. So x,y = columns, rows, NOT rows, columns. Here is corrected code:

x=0.0:0.5:2.0;
y=0.0:0.5:2.5;
T= [0.00 5.00 10.00 15.00 20.00;
  5.00 7.51 10.00 12.51 15.00;
  10.00 10.05 10.00 9.95 10.00;
  15.00 12.70 10.00 7.32 5.00;
  20.00 15.67 10.00 4.33 0.00;
  25.00 20.00 10.00 0.00 -5.00;];
whos y
whos x
size(T)
Tn= interp2(x,y,T,1.2,0.7)

[ggeneral]

but the question says y is columns. see question 2

[Image Analyst]

No it doesn't. x is columns, y is rows. Look again. Also, your T is wrong - doesn't match your textbook. It seems to be transposed or something.

[ggeneral]

i didnt need to use the semi-columns? when i ran it the table appeared like that on matlab.. im confused

[ggeneral]

ok i figured it out...thank you..im really slow

[Image Analyst]

They show a 5 row by 6 column table. You have a 6 row by 5 column table. And, no, semicolons are not required when writing out a table on multiple lines.

Answer 2

[Star Strider]

@George — As I read Problem 2, you transposed the table. It’s supposed to be (5x6). Yours is (6x5). Transpose ‘T’ (use the (') transpose operator to avoid retyping it) and your code should work.

y=0.0:0.5:2.0;
x=0.0:0.5:2.5;
T= [0.00 5.00 10.00 15.00 20.00;
    5.00 7.51 10.00 12.51 15.00;
    10.00 10.05 10.00 9.95 10.00;
    15.00 12.70 10.00 7.32 5.00;
    20.00 15.67 10.00 4.33 0.00;
    25.00 20.00 10.00 0.00 -5.00;];

T = T';

Tn= interp2(x,y,T,1.2,0.7)

produces:

Tn =

      10.6660