Please what did i do wrong here..using interp2

2015 4 11
2 个回答
更新时间：2015 4 11
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0 个投票

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)

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回答（2 个）

Image Analyst
Image Analyst 2015-4-11

0 个投票

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)

5 个评论
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ggeneral
ggeneral 2015-4-11
but the question says y is columns. see question 2
Image Analyst
Image Analyst 2015-4-11
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
ggeneral 2015-4-11
i didnt need to use the semi-columns? when i ran it the table appeared like that on matlab.. im confused
ggeneral
ggeneral 2015-4-11
ok i figured it out...thank you..im really slow
Image Analyst
Image Analyst 2015-4-11
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.

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Star Strider
Star Strider 2015-4-11

0 个投票

@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

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