Scaling an array by a certain number so that the area under the curve equals a fixed number

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Christina Hong
Christina Hong 2020-9-4
编辑： David Goodmanson 2020-9-4
Hi friends,
Say if I have an array Pyy consisting of 1000 elements. I want the area under the curve (x, Pyy) of this array to equal a fixed number, lets call this number 30.
I would like to do this by scaling the Pyy term to create a NEW vector (PyyNEW) (scaled from Pyy) which fits this criteria, so:
trapz(x, PyyNEW) = 30
How do I achieve this? SO far I have this code but doesnt seem to work:
syms a; %create a variable to solve algebraically
for i = 1:1000;
PyyNEW(i,1) = pyy(i,1)*a;
end
eqn = trapz(x, PyyNEW, 1) == 30;
sola = solve(eqn, a);

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回答（1 个）

David Goodmanson
David Goodmanson 2020-9-4
编辑：David Goodmanson 2020-9-4
HI Christina,
A = trapz(x,pyy) % find the unscaled area
pyy_new = pyy*(30/A);
trapz(x,pyy_new) % this will equal 30

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