How to calculate mean and standard deviation

Hi everyone, want to ask.

If I have set of data let say

X = [23,43, 45,90,15,41,71,29,45,52,32];

How to calculate the mean and standard deviation?

Answer 1

[Star Strider]

Mean: mean

Standard Deviation: std

[mohd akmal masud]

Oh so simple. Thank you star strider

[Star Strider]

My pleasure.

If my Answer helped you solve your problem, please Accept it!

[mohd akmal masud]

But std not give the value

[mohd akmal masud]

My data must be single not double. What means?

[Star Strider]

This works when I run it:

X = [23,43, 45,90,15,41,71,29,45,52,32];
Xmean = mean(X)                             % Double
Xstd = std(X)                               % Double
Xmean = single(mean(X))                     % Single
Xstd = single(std(X))                       % Single

producing:

Xmean =
  44.181818181818180

Xstd =
  21.381385277002899


Xmean =
  single
  44.1818199

Xstd =
  single
  21.3813858

[Image Analyst]

Mohd, you say your data must be single. That's an error you'll get if your data is uint8, like it came from an image, and try to use std() -- it will say your data must be single or double. So just cast your data to single or double and it will work fine:

X = uint8([23,43, 45,90,15,41,71,29,45,52,32])
meanX = mean(single(X))
stdX = std(single(X))

X =

1×11 uint8 row vector

23 43 45 90 15 41 71 29 45 52 32

meanX =

single

44.18182

stdX =

single

21.38139

[mohd akmal masud]

Thank you star strider and image Analyst. Will try tonight.

[Star Strider]

As always, our pleasure!

[Behzad Hosseinzadeh]

the standard deviation of those valuse are 20.386350967869, why MATLAB returns 21.38139?

[Image Analyst]

As you know, there are two standard deviations

1. the standard deviation of the sample
2. the standard deviation of the population

If you want the non-default formula, you have to tell it:

X = [23,43, 45,90,15,41,71,29,45,52,32];
sd = std(X) % Default
s0 = std(X, 0)
s1 = std(X, 1)

sd =

21.3813852770029

s0 =

21.3813852770029

s1 =

20.3863509678688

S = std(A,w) specifies a weighting scheme for any of the previous syntaxes. When w = 0 (default), S is normalized by N-1. When w = 1, S is normalized by the number of observations, N. w also can be a weight vector containing nonnegative elements. In this case, the length of w must equal the length of the dimension over which std is operating.

Answer 2

[MD Ashraful Islam]

mean(X)

std(X)