How to calculate MATLAB linspace function by hand

Question

There is a function named linspace in matlab and splits interval in given range. For example:

>> x = linspace(-10,5, 10)

x =

  -10.0000   -8.3333   -6.6667   -5.0000   -3.3333   -1.6667         0    1.6667    3.3333    5.0000

How can I find x(4) by doing calculations by hand ?

Type `open linspace` and see its code – Luis Mendo Nov 08 '14 at 19:50 — Luis Mendo, Nov 08 '14 at 19:50

score 5 · Accepted Answer · edited May 23 '17 at 12:27

This seems to work -

x = linspace(-10,5, 10)

start = -10;
stop = 5;
num_elements = 10;
index = 4;

out = start + (index-1)*(stop - start)./(num_elements-1)

Output -

x =
  -10.0000   -8.3333   -6.6667   -5.0000   -3.3333   -1.6667    0    1.6667 ...
out =
    -5

Thus, (stop - start)./(num_elements-1) would be the stepsize.

So, if you want the complete array, do this -

complete_array = start : (stop - start)./(num_elements-1) :stop

But, be careful of the floating point precision issues if you are comparing these results against the linspace results - What is the advantage of linspace over the colon “:” operator?.

1 Answers1