Plot for different values
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Hi, I'm trying to vary the value of Q but the values aren't changing.
HfTOTAL = 26.8708
Hg = 30
Q = 0:50:450;
K = HfTOTAL./Q.^1.852
Hm = Hg + K.*Q.^1.852 % m
KQ = K.*Q.^1.852
plot(Q,Hm,'k','LineWidth',2)
采纳的回答
Walter Roberson
2021-8-15
Just for fun, let is assign Q.^1.852 to a variable, say Q18
HfTOTAL = 26.8708
Hg = 30
Q = 0:50:450;
Q18 = Q.^1.852;
K = HfTOTAL./Q18;
So K is something divided by Q18
Hm = Hg + K.*Q18 % m
And there you take K times Q18. But Q is something divided by Q18, so except for loss of precision due to round-off error, or inf or nan effects, then K*Q18 is going to be the same as the something that was then divided by Q18. So
Hm = Hg + repmat(HfTotal, 1, length(Q));
but that's just a repeated constant
KQ = K.*Q18
Again that is just the same as repmat(HfTotal, 1, length(Q)); so it is just a repeated constant.
plot(Q,Hm,'k','LineWidth',2)
You plot the different Q values with the repeated constant on the Y axes.
5 个评论
Right, I was not suggesting to you that you use repmat, I was saying that your code was the same as if you used repmat.
Suppose you have
Q = 1:3
HfTOTAL = 6
K = HfTOTAL./Q
So a constant divided by the different Q values
Hm = K.*Q
And then you multiply by the different Q values.. the result is going to be the same as the constant repeated to the same length as Q. (A/B)*B gives back A (copied according to the size of B)
You are always going to get a straight line as long as you have
K = HfTOTAL./Q.^1.852
Hm = Hg + K.*Q.^1.852
where you are multiplying by the exact same thing you divided by.
Luccas S.
2021-8-15
Using a for loop will not help.
HfTotal = 6
for Q = 1 : 3
K(Q) = HfTotal./Q
end
for Q = 1 : 3
Hm(Q) = K(Q) .* Q
end
The problem is that you are multipling by the exact same thing you are dividing by.
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