Calculating Means and Standard Deviations over a range without duplication

Cheuk Ki Man

Join Date: Jun 2018

Posts: 2
#1

Calculating Means and Standard Deviations over a range without duplication

22 Jun 2018, 10:03

Hello,

I am a novice in STATA and I am struggling to calculate the mean and standard deviations of a range in a non-overlapping way.

Example as follows:

Group A B C

1 30 45 60

1 44 70 26

1 25 30 35

1 10 27 46

1 42 24 10

2 98 77 66

2 65 33 23

2 23 24 27

2 20 12 10

2 60 45 28

So basically I would like to calculate the mean and sd of Group 1 (3*5 blocks) and 2 (3*5 blocks) for A:C.

Please advise.

Thanks

Kind Regards,
Jacky
Tags: None

Nick Cox

Join Date: Mar 2014
Posts: 35426

22 Jun 2018, 11:33

Here are two ways to do it:

1. Classic. A loop over variables using egen

2. Modern. Install rangestat using ssc inst rangestat

Code:

clear 
input Group    A    B    C
1    30    45    60
1    44    70    26
1    25    30    35
1    10    27    46
1    42    24    10
2    98    77    66
2    65    33    23
2    23    24    27
2    20    12    10
2    60    45    28
end 

foreach v in A B C { 
    egen mean`v' = mean(`v'), by(Group)
    egen sd`v' = sd(`v'), by(Group)
}

rangestat (mean) A B C (sd) A B C, int(Group 0 0)

Code:

. list G *mean*

     +----------------------------------------------------------+
     | Group   meanA   meanB   meanC   A_mean   B_mean   C_mean |
     |----------------------------------------------------------|
  1. |     1    30.2    39.2    35.4     30.2     39.2     35.4 |
  2. |     1    30.2    39.2    35.4     30.2     39.2     35.4 |
  3. |     1    30.2    39.2    35.4     30.2     39.2     35.4 |
  4. |     1    30.2    39.2    35.4     30.2     39.2     35.4 |
  5. |     1    30.2    39.2    35.4     30.2     39.2     35.4 |
     |----------------------------------------------------------|
  6. |     2    53.2    38.2    30.8     53.2     38.2     30.8 |
  7. |     2    53.2    38.2    30.8     53.2     38.2     30.8 |
  8. |     2    53.2    38.2    30.8     53.2     38.2     30.8 |
  9. |     2    53.2    38.2    30.8     53.2     38.2     30.8 |
 10. |     2    53.2    38.2    30.8     53.2     38.2     30.8 |
     +----------------------------------------------------------+

. 
. list G *sd* 

     +----------------------------------------------------------------+
  1. | Group |      sdA |      sdB |      sdC |      A_sd |      B_sd |
     |     1 | 13.82751 | 19.01841 | 19.04731 | 13.827509 | 19.018412 |
     |----------------------------------------------------------------|
     |                                C_sd                            |
     |                            19.04731                            |
     +----------------------------------------------------------------+

     +----------------------------------------------------------------+
  2. | Group |      sdA |      sdB |      sdC |      A_sd |      B_sd |
     |     1 | 13.82751 | 19.01841 | 19.04731 | 13.827509 | 19.018412 |
     |----------------------------------------------------------------|
     |                                C_sd                            |
     |                            19.04731                            |
     +----------------------------------------------------------------+

     +----------------------------------------------------------------+
  3. | Group |      sdA |      sdB |      sdC |      A_sd |      B_sd |
     |     1 | 13.82751 | 19.01841 | 19.04731 | 13.827509 | 19.018412 |
     |----------------------------------------------------------------|
     |                                C_sd                            |
     |                            19.04731                            |
     +----------------------------------------------------------------+

     +----------------------------------------------------------------+
  4. | Group |      sdA |      sdB |      sdC |      A_sd |      B_sd |
     |     1 | 13.82751 | 19.01841 | 19.04731 | 13.827509 | 19.018412 |
     |----------------------------------------------------------------|
     |                                C_sd                            |
     |                            19.04731                            |
     +----------------------------------------------------------------+

     +----------------------------------------------------------------+
  5. | Group |      sdA |      sdB |      sdC |      A_sd |      B_sd |
     |     1 | 13.82751 | 19.01841 | 19.04731 | 13.827509 | 19.018412 |
     |----------------------------------------------------------------|
     |                                C_sd                            |
     |                            19.04731                            |
     +----------------------------------------------------------------+

     +----------------------------------------------------------------+
  6. | Group |      sdA |      sdB |      sdC |      A_sd |      B_sd |
     |     2 | 32.42992 | 24.83344 | 20.94517 | 32.429924 | 24.833445 |
     |----------------------------------------------------------------|
     |                                C_sd                            |
     |                           20.945167                            |
     +----------------------------------------------------------------+

     +----------------------------------------------------------------+
  7. | Group |      sdA |      sdB |      sdC |      A_sd |      B_sd |
     |     2 | 32.42992 | 24.83344 | 20.94517 | 32.429924 | 24.833445 |
     |----------------------------------------------------------------|
     |                                C_sd                            |
     |                           20.945167                            |
     +----------------------------------------------------------------+

     +----------------------------------------------------------------+
  8. | Group |      sdA |      sdB |      sdC |      A_sd |      B_sd |
     |     2 | 32.42992 | 24.83344 | 20.94517 | 32.429924 | 24.833445 |
     |----------------------------------------------------------------|
     |                                C_sd                            |
     |                           20.945167                            |
     +----------------------------------------------------------------+

     +----------------------------------------------------------------+
  9. | Group |      sdA |      sdB |      sdC |      A_sd |      B_sd |
     |     2 | 32.42992 | 24.83344 | 20.94517 | 32.429924 | 24.833445 |
     |----------------------------------------------------------------|
     |                                C_sd                            |
     |                           20.945167                            |
     +----------------------------------------------------------------+

     +----------------------------------------------------------------+
 10. | Group |      sdA |      sdB |      sdC |      A_sd |      B_sd |
     |     2 | 32.42992 | 24.83344 | 20.94517 | 32.429924 | 24.833445 |
     |----------------------------------------------------------------|
     |                                C_sd                            |
     |                           20.945167                            |
     +----------------------------------------------------------------+

Comment

Marcos Almeida

Join Date: Apr 2014
Posts: 4047

22 Jun 2018, 13:21

Maybe this approach (reshaping long) would also be helpful:

Code:

 d

. rename ( A B C) (v1 v2 v3)

. gen id = _n

. reshape long v, i(id) j(step)
(note: j = 1 2 3)

Data                               wide   ->   long
-----------------------------------------------------------------------------
Number of obs.                       10   ->      30
Number of variables                   5   ->       4
j variable (3 values)                     ->   step
xij variables:
                               v1 v2 v3   ->   v
-----------------------------------------------------------------------------

. label define mylab 1 "A" 2 "B" 3 "C"

. label values step mylab

. drop id

. by Group step, sort : egen float mymean1 = mean(v)

. by Group step, sort : egen float mysd1 = sd(v)

. list

     +----------------------------------------+
     | step   Group    v   mymean1      mysd1 |
     |----------------------------------------|
  1. |    A       1   42      30.2   13.82751 |
  2. |    A       1   30      30.2   13.82751 |
  3. |    A       1   44      30.2   13.82751 |
  4. |    A       1   10      30.2   13.82751 |
  5. |    A       1   25      30.2   13.82751 |
     |----------------------------------------|
  6. |    B       1   45      39.2   19.01841 |
  7. |    B       1   24      39.2   19.01841 |
  8. |    B       1   27      39.2   19.01841 |
  9. |    B       1   30      39.2   19.01841 |
 10. |    B       1   70      39.2   19.01841 |
     |----------------------------------------|
 11. |    C       1   10      35.4   19.04731 |
 12. |    C       1   35      35.4   19.04731 |
 13. |    C       1   46      35.4   19.04731 |
 14. |    C       1   60      35.4   19.04731 |
 15. |    C       1   26      35.4   19.04731 |
     |----------------------------------------|
 16. |    A       2   23      53.2   32.42992 |
 17. |    A       2   65      53.2   32.42992 |
 18. |    A       2   20      53.2   32.42992 |
 19. |    A       2   60      53.2   32.42992 |
 20. |    A       2   98      53.2   32.42992 |
     |----------------------------------------|
 21. |    B       2   45      38.2   24.83344 |
 22. |    B       2   12      38.2   24.83344 |
 23. |    B       2   33      38.2   24.83344 |
 24. |    B       2   77      38.2   24.83344 |
 25. |    B       2   24      38.2   24.83344 |
     |----------------------------------------|
 26. |    C       2   28      30.8   20.94517 |
 27. |    C       2   23      30.8   20.94517 |
 28. |    C       2   66      30.8   20.94517 |
 29. |    C       2   27      30.8   20.94517 |
 30. |    C       2   10      30.8   20.94517 |
     +----------------------------------------+

Best regards,

Marcos

Comment

Cheuk Ki Man

Join Date: Jun 2018

Posts: 2
#4

25 Jun 2018, 03:52

Apologies guys, I have tired it out again. the numbers that returned are the averages of 1Column*5Rows --> 30.2 for Group 1 A.

what I would like to achieve is to calculate the averages for Group 1 regardless of Group A,B, C.

For group 1, it would be (30+44+25+10+42+45+70+30+27+24+60+26+35+46+10)/15 = 34.933333...

Using the classic looping method. It doesn't work.

Please advise.

Thanks

Kind Regards,
Jacky

Last edited by Cheuk Ki Man; 25 Jun 2018, 04:11.
Comment
Marcos Almeida

Join Date: Apr 2014

Posts: 4047
#5

25 Jun 2018, 06:36

I believe you can handle this easily. Just exclude ‘step’ from the - egen - command shared to you above.

Best regards,

Marcos
Comment
Nick Cox

Join Date: Mar 2014

Posts: 35426
#6

25 Jun 2018, 06:45

The average of A or B or C is just the average of A + B + C divided by 3.
Comment

Marcos Almeida

Join Date: Apr 2014
Posts: 4047

25 Jun 2018, 14:52

Nick gave the direct approach. If you wish to use - egen - for that matter, you just need to type:

Code:

. by Group, sort : egen float mymean2 = mean(v)
. by Group, sort : egen float mysd2 = sd(v)
. list Group v mymean2 mysd2

     +----------------------------------+
     | Group    v    mymean2      mysd2 |
     |----------------------------------|
  1. |     1   44   34.93333   16.61955 |
  2. |     1   42   34.93333   16.61955 |
  3. |     1   30   34.93333   16.61955 |
  4. |     1   25   34.93333   16.61955 |
  5. |     1   10   34.93333   16.61955 |
     |----------------------------------|
  6. |     1   45   34.93333   16.61955 |
  7. |     1   27   34.93333   16.61955 |
  8. |     1   30   34.93333   16.61955 |
  9. |     1   24   34.93333   16.61955 |
 10. |     1   70   34.93333   16.61955 |
     |----------------------------------|
 11. |     1   60   34.93333   16.61955 |
 12. |     1   46   34.93333   16.61955 |
 13. |     1   35   34.93333   16.61955 |
 14. |     1   26   34.93333   16.61955 |
 15. |     1   10   34.93333   16.61955 |
     |----------------------------------|
 16. |     2   23   40.73333   26.36412 |
 17. |     2   98   40.73333   26.36412 |
 18. |     2   60   40.73333   26.36412 |
 19. |     2   65   40.73333   26.36412 |
 20. |     2   20   40.73333   26.36412 |
     |----------------------------------|
 21. |     2   45   40.73333   26.36412 |
 22. |     2   12   40.73333   26.36412 |
 23. |     2   33   40.73333   26.36412 |
 24. |     2   24   40.73333   26.36412 |
 25. |     2   77   40.73333   26.36412 |
     |----------------------------------|
 26. |     2   66   40.73333   26.36412 |
 27. |     2   23   40.73333   26.36412 |
 28. |     2   27   40.73333   26.36412 |
 29. |     2   10   40.73333   26.36412 |
 30. |     2   28   40.73333   26.36412 |
     +----------------------------------+

Best regards,

Marcos

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Calculating Means and Standard Deviations over a range without duplication

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