Returning negative value of element in vector

Hi!

I need to return every second element in a vector as negative, how do I do it?

for example; v=[1 4 -0.3 0.2 4 7 14 -25 -0.003 245]

should be vnew=[1 -4 -0.3 -0.2 4 -7 14 25 -0.003 -245]

Answer 1

[Ameer Hamza]

v=[1 4 -0.3 0.2 4 7 14 -25 -0.003 245];
v(2:2:end) = -v(2:2:end)

Result

>> v
v =
    1.0000   -4.0000   -0.3000   -0.2000    4.0000   -7.0000   14.0000   25.0000   -0.0030 -245.0000

Read about indexing in MATLAB: https://www.mathworks.com/company/newsletters/articles/matrix-indexing-in-matlab.html

[Joel Bovin]

Thank you! I read the indexing beforehand to try to solve it myself but I didn't understand it well enough, thank you for the help!

[Ameer Hamza]

I am glad to be of help!