Possible to simplify vector expression?

While writing a script...

My goal was to have a vector defined with a long list of terms that show the difference in adjacent temperatures for an already defined column of values(male_temperature).

temp_diff = [(male_temperature(1) - male_temperature(2)) (male_temperature(2) - male_temperature(3)) all the way to (male_temperature(23) - male_temperature(24))]

after much trouble and research, managed to simplify it to:

for k = 1:23;
    v = genvarname('d', who);
    eval([v ' = male_temperature(k) - male_temperature(k+1)']);
end
temp_diff = [d d1 d2 d3 d4 d5 d6 d7 d8 d9 d10 d11 d12 d13 d14 d15 d16 d17 d18 d19 d20 d21 d22]
clear d d1 d2 d3 d4 d5 d6 d7 d8 d9 d10 d11 d12 d13 d14 d15 d16 d17 d18 d19 d20 d21 d22

Is there a better way to simplify this or a different way of doing this. Is there any way to better simplify the vector expression (temp_diff) at all? It is inefficient having to type out all these variables.

[John Mahoney]

Do you want this?

temp_diff = diff(male_temperature)

Actually, since you define temp_diff as [mt(1) - mt(2), …] I think you want

temp_diff = -diff(male_temperature)

Answer 1

[Devin Mair]

for step = 1:23

temp_diff(step) = male_temperature(step) - male_temperature(step +1);

end

I think this would work for you, based on my understanding of the problem.

[Ryan]

The outputs for both my version look strange and different than usual.

Typically I will get an ouput that looks like this:

temp_diff =

       2     3     4     5     6     7     8     9    10    11

But with both my code and yours, I get

temp_diff =

    Columns 1 through 6

      0.0600    0.0200   -0.0100         0   -0.1100   -0.0700

    Columns 7 through 12

     -0.0700   -0.0200    0.0600   -0.1600   -0.1000   -0.1000

The numbers aren't really relevant my question is about the style change. Do they behave the same, how can i convert to the form that I am used to. Is it even necessary?

[John Mahoney]

Ryan, It looks like both outputs are a single row of numbers. The reason the second output has "Columns 1 through 6" etc is because of the length of the array on the screen. Try

a = 2:30

and you will see the same thing.

Btw, take a look at my answer to your problem above. I think it has several advantages. You don't need to know the length of the array, and therefore you can't screw up looping over the correct number (-1). Also, for very large data sets it can be faster. More importantly, it is just good to be aware of the functions within Matlab that can perform simple tasks on entire arrays "at once" - so called "vectorized" functions. Good luck - John

[Devin Mair]

Using the built in function is definitely preferable. John's method should be used in this case.