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logspace equivalent and sin(x) [solved]

Asked by Giacomo Lorenzi on 10 Nov 2019
Latest activity Commented on by Steven Lord
on 11 Nov 2019
Hello, I have to solve a couple of exercises; the first one asks me to write with ":" the equivalents of this:
x=linspace(0, 10, 5);
x=linspace(-5, 5);
x=logspace(1, 3, 3);
x=logspace(1, 3, 5);
I solved the first by myself ( x=[0:2.5:10] ) because it's easy, but I really can't understand the others; actually I don't just want to solve the exercises but I want to understand if there is actually a method and how it is done.
Second one is this: A = {sin(x), x=1,2, ,1000}, I have to find how many elements of A are bigger than 1/2 using function SUM; actually I don't know that writing, I just started using Matlab, but even Matlab gives me an error, so maybe I thought it was wrong written; any guesses?

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3 Answers

Answer by Stephan
on 10 Nov 2019
 Accepted Answer

x = 10.^(1:3) % x=logspace(1, 3, 3)
result = sum(A>0.5) % Number of elements in A bigger than 0.5

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Stephan
on 10 Nov 2019
x = 10.^(1:0.5:3) % x=logspace(1, 3, 5)
Thanks a lot!

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Answer by JESUS DAVID ARIZA ROYETH on 10 Nov 2019

a=1;
b=3;
c=3;
logspace(a, b, c)==10.^(1:(b-a)/(c-1):b) %are equivalent
on the other hand
x=1:1000;
A=sin(x);
total=sum(A>1/2)

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Answer by Giacomo Lorenzi on 10 Nov 2019

Thanks guys, you were really helpful. However I still don't know how to solve the last
x = logspace(1, 3, 5)
it seems very tricky to me; the formula used for the previous one was pretty "standard", this is more "strange". Don't you know how to solve this too?

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You could "cheat" a little and look at what logspace does.
type logspace.m
I'm using type rather than edit to avoid accidentally modifying logspace. It's short enough that this won't display too much in the Command Window.

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