minimum of array of floats in python

Question

How can I find minimum of array of floats in Python? The min() or array.min() did not work. Here is the code:

import numpy as np

z=np.array([[ -4.26141957e-01],
       [ -2.26582552e-01],
       [ -7.28807682e-03],
       [  2.72843324e-02],
       [ -5.59146620e-02],
       [ -2.06062340e-05],
       [  1.06954166e-09],
       [ -6.34170623e-01],
       [  5.07841198e-02],
       [ -1.89888605e-04]])

z_min=z.min()

which gives z_min = -0.63417062312627426. I am a Matlab user so this is confusing to me...

Yo what do you want to happen? That answer looks correct to me — Colonel Panic
– Colonel Panic, Commented May 22, 2013 at 13:31
Yeah... it's the right answer. Maybe you want z[np.abs(z).argmin()] the number with the least magnitude? — Geoff
– Geoff, Commented May 22, 2013 at 13:32
That looks correct. Are you forgetting to look at the negative powers of ten, which reduce the magnitude of the numbers? — Steven Rumbalski
– Steven Rumbalski, Commented May 22, 2013 at 13:33
@Makaroni -0.634 < -0.0559 is true, isn't it? Then -0.634 is smaller — that's how min() works. — user4815162342
– user4815162342, Commented May 22, 2013 at 13:58
-10 < -1 Right? Try it in Matlab, too. You'll get the same result. It's just how negative numbers work. — Geoff
– Geoff, Commented May 22, 2013 at 14:00

chenaren · Accepted Answer · 2013-05-23 00:24:02Z

5

z_min = -0.63417062312627426 looks like the right answer. Be careful about scientific notation.

edited May 23, 2013 at 0:24

answered May 22, 2013 at 13:32

chenaren

2,2781 gold badge21 silver badges25 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Geoff · Accepted Answer · 2013-05-22 13:44:06Z

3

np.min() returns the smallest number, or the "largest" negative number (if there are any). In this case the entry at index 7 is the minimum entry. It is -6.34 * 10^-1 in scientific notation, or -0.634... in long-hand.

Printing all in long-hand

Perhaps this will help:

print "\n".join(["%+0.10f" % e for e in z])

-0.4261419570
-0.2265825520
-0.0072880768
+0.0272843324
-0.0559146620
-0.0000206062
+0.0000000011
-0.6341706230
+0.0507841198
-0.0001898886

To verify your answer

The following will show that only one entry has this minimum value.

z <= z.min()

array([[False],
       [False],
       [False],
       [False],
       [False],
       [False],
       [False],
       [ True],
       [False],
       [False]], dtype=bool)

One more example

The number closest to zero can be found like this:

z[np.abs(z).argmin()]

Which is 1.06954166e-09 = 1.069 * 10^-09 in scientific notation or 0.000000000106... in long-hand.

edited May 22, 2013 at 13:44

answered May 22, 2013 at 13:36

Geoff

8,1853 gold badges37 silver badges44 bronze badges

1 Comment

Geoff Over a year ago

By the way, I guess you probably didn't need all this. I just figured it may help future readers.

Collectives™ on Stack Overflow

minimum of array of floats in python

2 Answers 2

Comments

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related