how do i reverse a vector

so far i have this

function [Vout]=reverse(Vin)

Answer 1

[Youssef Khmou]

hi,

To reverse a vector try the function ' wrev' , here is an example :

 r=wrev(1:4)

If you to control the degree of reverse/shifting try 'circshift' function.

[Matthew Eicholtz]

I like this solution. Does anybody know how fliplr and wrev differ in this particular case? Is one more computationally expensive than the other?

[Andrei Bobrov]

wrev(vect) -> vect(end:-1:1)

please try:

>> open wrev

Answer 2

[Royi Avital]

This might work as well (For 1D Vectors):

vReversed = v(end:-1:1);

Good luck!

[Shweta Kanitkar]

v(end:-1:1) subtracts each element from v(end) by 1.

[Walter Roberson]

Matt Eicholtz points out that Shweta's comment is incorrect; no subtraction is done, only indexing.

[Cyrus David Pastelero]

This is what I am looking for. Thank you.

Answer 3

[Walter Roberson]

fliplr() or flipud()

... But I suspect this is a class assignment. You will need to use your knowledge of MATLAB indexing and looping to work out your assignments for yourself.

Answer 4

[goga]

use fliplr()

Answer 5

[Varshitha Gouri]

v = [1 2 3 4 5];
reversed = flip(v);
disp(reversed);

     5     4     3     2     1

Answer 6

[DEVARAKONDA STEPHEN]

v = [10, 20, 30, 40, 50];

n = length(v);

for i = 1:n
    rev(i) = v(n - i + 1);
end

disp('Reversed vector:');

Reversed vector:

disp(rev);

    50    40    30    20    10

[Stephen23]

Doing this in a loop is very inefficient: avoid this approach!

[Steven Lord]

It's also incorrect in some cases, since rev was not preallocated.

v = (1:5).'

v = 5×1

1 2 3 4 5

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n = length(v);
for i = 1:n
    rev(i) = v(n - i + 1);
end
rev

rev = 1×5

5 4 3 2 1

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whos v rev

  Name      Size            Bytes  Class     Attributes

  rev       1x5                40  double              
  v         5x1                40  double              

In this case rev is the wrong size/shape! Compare with one of the recommended approach:

flippedV = flip(v)

flippedV = 5×1

5 4 3 2 1

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whos flippedV v

  Name          Size            Bytes  Class     Attributes

  flippedV      5x1                40  double              
  v             5x1                40  double              

In fact, the lack of preallocation may make the code error. Let me show the recommended approach first then show the error case. Because the previous section of code effectively "preallocated" rev, I need to clear it to simulate running the code in isolation.

v = zeros(1, 0);
flippedV = flip(v)

flippedV =

  1×0 empty double row vector

clear rev % Simulate running the code without preallocation
n = length(v);
for i = 1:n
    rev(i) = v(n - i + 1);
end
rev % doesn't exist, so this will error

Unrecognized function or variable 'rev'.