Can anyone tell what is this line doing
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Kamil Kacer
il 23 Nov 2020
Commentato: Kamil Kacer
il 23 Nov 2020
It seems these two first lines two the exact same thing can anyone help
I cannot figure out what they are doing
a = d{1}(f(1,2));
a = f(1,2);
...
f = [1 2 4];
d = {[4 2 1] [4 1 2] [4 3 5]};
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John D'Errico
il 23 Nov 2020
Modificato: John D'Errico
il 23 Nov 2020
You asked again, why you cannot use f(1,3), instead of f(1,2).
LOOK CAREFULLY AT WHAT YOU HAVE. TAKE IT ONE STEP AT A TIME.
f = [1 2 4];
d = {[4 2 1] [4 1 2] [4 3 5]};
Now, what is f(1,3)? TRY IT!
f(1,3)
It is the number 4. How are you using it? As an index into a cell of the cell array d. So what is d{1}?
d{1}
Does d{1} have a 4th element? NO.
Why was this not a problem with f(1,2)? Because f(1,2) is 2.
d{1}(f(1,2))
d{1}(f(1,3))
The latter case fails because you cannot access the 4th element of a vector that has only 3 elements.
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John D'Errico
il 23 Nov 2020
Excellent.
For most problems in MATLAB where you need to understand a complicated line of code, you take apart the line from the inside and work out. Figure out what the inside piece is doing. Then look backwards and outwards. In this case, it is perhaps not fully obvious, that (f(1,2)) was an index into what came before.
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KSSV
il 23 Nov 2020
f = [1 2 4]; % this is an array can be access by f (i) where i = 1,2,3
d = {[4 2 1] [4 1 2] [4 3 5]}; % this is a cell array, can be access by d {i} where i = 1,2,3
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