0 个投票

Hello,
I am trying to make an if statement that will check the values of vector "T_m", element by element, with vector "T_s". All variables are vectors of the same length 10080x1. The result should be a vector as well. The values that "P_actual" attain are always equal to "P", even though there are times that T_m is higher than T_s.
Here is the code:
if T_m > T_s
P_actual = P - 0.3*(T_m - T_s);
else
P_actual = P;
end
I would appreciate any sort of help or tips!

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Stephen23
Stephen23 2019-5-25
编辑：Stephen23 2019-5-25

0 个投票

You cannot use if like that to operate element-wise on arrays (read the if help to know what your code is actually doing). You could use a loop, but that would be pointlessly complex for this simple task.
Method one: indexing:
P_actual = P - 0.3*(T_m-T_s);
idx = T_m>T_s;
P_actual(~idx) = P(~idx)
Method two: max:
P_actual = P - 0.3*max(0,T_m-T_s)
I recommend using the max method.

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Thank you so much Stephen! The max function made things quite easy. However, there are still times at which I need to compare values between arrays.
For example:
if A > 0
will be true when each element of A is above 0. Similarly if I set A > B (both are vectors), then the statement would be true only if all elements of A are bigger than B. How can modify this to get a true or false statement for each element respectively?
Forgive me for the vagueness, but my fundamentals are quite weak.
Nevermind, I managed to do it with a combination of "for" and "if" loop statements. Thanks again!
Stephen23
Stephen23 2019-5-27
Rather than using a loop, use logical indexing, as I showed in my answer.

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KALYAN ACHARJYA
KALYAN ACHARJYA 2019-5-25
编辑：KALYAN ACHARJYA 2019-5-25

0 个投票

Your code doing the same
T_m=randi(6,1);
T_s=rand(6,1);
P=rand(6,1);
if T_m > T_s
P_actual = P - 0.3*(T_m - T_s);
else
P_actual = P;
end
Example 1: Here T_m>T_s
T_m =
1 2 3 4 5 6
T_s =
0.7224
0.1499
0.6596
0.5186
0.9730
0.6490
P =
0.8003
0.4538
0.4324
0.8253
0.0835
0.1332
P_actual =
0.7171 0.4171 0.1171 -0.1829 -0.4829 -0.7829
0.1988 -0.1012 -0.4012 -0.7012 -1.0012 -1.3012
0.3303 0.0303 -0.2697 -0.5697 -0.8697 -1.1697
0.6809 0.3809 0.0809 -0.2191 -0.5191 -0.8191
0.0754 -0.2246 -0.5246 -0.8246 -1.1246 -1.4246
0.0279 -0.2721 -0.5721 -0.8721 -1.1721 -1.4721
Example 2: Here T_m<=T_s (Else Condition P_actual = P)
T_m =
0.1734
0.3909
0.8314
0.8034
0.0605
0.3993
T_s =
1 2 3 4 5 6
P =
0.5269
0.4168
0.6569
0.6280
0.2920
0.4317
P_actual =
0.5269
0.4168
0.6569
0.6280
0.2920
0.4317

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