Hash-Object Programming in SAS...Hash-Object Programming in SAS Malcolm MacRae, AESO Sean McCarthy, ENMAX 0. INTRODUCTION TO HASH OBJECTS Malcolm MacRae 1. Introduction to Hash Objects

Hash-Object Programming in SAS

Malcolm MacRae, AESO

Sean McCarthy, ENMAX

0

INTRODUCTION TO HASH OBJECTSMalcolm MacRae

1

Introduction to Hash Objects

• What is a hash object?

– Adelson-Velsky Landis tree

– In-memory object

– Associates key value with specific data values

• Why is it important?

– Provides look-up functionality

– Similar to exact-match VLOOKUP function in Excel

2

Presentation Overview

• Create a hash object

• Populate a hash object

• Use a hash object

3

SAS Code Template

data work.hash_demo;

/* Define return code */

length rc 8;

/* Create hash object */

/* Populate hash object */

/* Use hash object */

/* Terminate hash object */

rc = h.delete();

run;

4


• Create a hash object

– Hash object structure

– Multi-data hash objects



5

Create a Hash Object

6

One key variable Multiple key variables

One data variable Simple hash object Composite-key hash object

Multiple data variables Multi-variable hash object Complex hash object

• Hash object structure is defined by:

1. Key variables; and,

2. Data variables

• Four types of hash object structure:

Simple Hash Object

/* Define variables */

length key data 8;

/* Initialize hash object */

declare hash h();

/* Define hash object */

h.defineKey(’key’);

h.defineData(’data’);

h.defineDone();

/* Initialize variables */

call missing(key,data);

7

datakey

Hash Object h

Program Data Vector

key data rc

Multi-Variable Hash Object


length key data1 data2 8;


declare hash h();



h.defineData(’data1’,’data2’);

h.defineDone();


call missing(key,data1,data2);

8

data1 data2key

Hash Object h

Program Data Vector

key data1 rcdata2

Composite-Key Hash Object


length key1 key2 data 8;


declare hash h();


h.defineKey(’key1’,’key2’);


h.defineDone();


call missing(key1,key2,data);

9

datakey2key1

Hash Object h

Program Data Vector

key1 key2 data rc

Complex Hash Object


length key1 key2 data1 data2 8;


declare hash h();




h.defineDone();


call missing(key1,key2,

data1,data2);

10

data1 data2key2key1

Hash Object h

Program Data Vector

key2 data1 data2 rckey1

Multi-Data Hash Objects

• Hash object by default

– Associates one key value with one data value

• Multi-data hash object

– Associates one key value with multiple data values

– Supports simple hash objects

– Supports multi-variable hash objects

– Supports composite-key hash objects

– Supports complex hash objects

11

key1key1

Simple Multi-Data Hash Object


length key data 8;


declare hash h(multidata:’y’);




h.defineDone();



12

datakey

Hash Object h

Program Data Vector

rc data key

key1key1 key1key1

Complex Multi-Data Hash Object


length key1 key2 data1 data2 8;






h.defineDone();


call missing(key1,key2,

data1,data2);

13

data1 data2key2key1

Hash Object h

Program Data Vector

rc data key


• Created a hash object


– Populate manually

– Populate from data set


14

Example: Modulus Function

• Remainder in integer division:

f(x) = x mod 3

• SAS function:

f(x) = mod(x, 3);

x f(x)

1 1

2 2

3 0

4 1

5 2

6 0

7 1

8 2

9 0

15

key1key1

Simple Multi-Data Hash Object


length key data 8;






h.defineDone();



16

datakey

Hash Object h

Program Data Vector

rc data key

Manually Populate Hash Object

/* Populate hash-object LUT. */

do data = 1 to 9;

key = mod(data,3);

rc = h.add();

end;

17

datakey

Hash Object h

Program Data Vector

rc data key

1 1

2 2

0 3

1 12 23 04 10

45 12



do data = 1 to 9;

key = mod(data,3);

rc = h.add();

end;

18

1

datakey

1

0

Hash Object h

Program Data Vector

rc data key

2 2

0 369

58

47

6 07 18 29 0

9



do data = 1 to 9;

key = mod(data,3);

rc = h.add();

end;

19

1

datakey

1

0 0

Hash Object h

Program Data Vector

rc data key

2 2

0 369

58

47

Populate Hash Object from Data Set

/* Create sample data set */

data work.lut;

do data = 1 to 9;

key = mod(data,3);

output;

end;

run;

data key

1 1

2 2

3 0

4 1

5 2

6 0

7 1

8 2

9 0

20

work.lut

Populate Hash Object from Data Set


length key data 8;

/* Initialize hash object. */

declare hash h(

dataset:'work.lut',

multidata:'y');


h.defineKey(key:'key');

h.defineData(data:'data');

h.defineDone();


call missing(key, data);

21

1

datakey

1

Hash Object h

Program Data Vector

rc data key

2 2

0 369

58

47



• Populated a hash object


– Hash-object look-up table

– Hash-object iterators

22

96

85

74

Hash-Object LUT

/* Perform look-up */

do key = -1 to 3;

rc = h.find();

do while (rc = 0);

output;

rc = h.find_next();

end;

end;

23

1

datakey

1

Hash Object h

Program Data Vector

rc data key

2 2

0 3

-1160038 00 3

69

69160038

Output Data Set

Hash-Object LUT

key data rc

0 3 0

0 6 0

0 9 0

1 1 0

1 4 0

1 7 0

2 2 0

2 5 0

2 8 0

24

Hash Object Iterator

• Iterates through hash object LUT

• Iterator methods:

– .first()

– .next()

– .prev()

– .last()

25

key1key1



length key data 8;






h.defineDone();



/* Hash-object iterator. */

declare hiter hit(’h’);

26

datakey

Hash Object h

Program Data Vector

rc data key

96

85

74

Hash-Object Iterator

/* Iterate through LUT */

rc = hit.first();

do until (rc = 0);

output;

rc = hit.next();

end;

27

1

datakey

1

Hash Object h

Program Data Vector

rc data key

2 2

0 3

30 6

6

9

9

0 2

Output Data Set

Hash Object LUT

key data rc

0 3 0

0 6 0

0 9 0

1 1 0

1 4 0

1 7 0

2 2 0

2 5 0

2 8 0


key data rc

3 0

6 0

9 0

2 0

5 0

8 0

1 0

4 0

7 0

28

key1key1

Ordered Hash Object Iterator


length key data 8;


declare hash h(

multidata:’y’,

ordered:’ascending’);



h.defineData(’key’,’data’);

h.defineDone();



/* Hash-object iterator. */

declare hiter hit(’h’);

29

datakey

Hash Object h

Program Data Vector

rc data key

Output Data Set

Hash-Object LUT

key data rc

0 3 0

0 6 0

0 9 0

1 1 0

1 4 0

1 7 0

2 2 0

2 5 0

2 8 0

Ordered Hash-Object Iterator

key data rc

0 3 0

0 6 0

0 9 0

1 1 0

1 4 0

1 7 0

2 2 0

2 5 0

2 8 0

30



• Populated a hash object

• Used a hash object

31

Additional Resources

• Burlew, Michelle. Hash Object Programming Made Easy. SAS Press.

32

APPLICATIONS OF HASH OBJECTSSean McCarthy

33

Join Customers Table with Sales Table

34

Item Sold Price Cust_ID

iPhone 7 $800 2

iPad Air $700 1

Customer_ID Name

1 Sean

2 Malcolm

Sales Table

Customers Table

data work.add_cust_name;

if _N_ = 1 then do;

declare hash cust(dataset: “work.Customers”);

cust.defineKey(“Customer_ID”);

cust.defineData(“Name”);

cust.defineDone();

end;

set work.Sales;

length Name $ 7;

if cust.find(key: Cust_ID) NE 0

then call missing(Name);

run;

Item Sold Price Cust_ID Name

iPhone 7 $800 2 Malcolm

iPad Air $700 1 Sean

New Table

No resource-intensive sorting required—explicit or implicit!

Aggregating with Hash Objects

35

data _NULL_;

declare hash rev();

rev.defineKey(“Name”);

rev.defineData(“Name”, “Revenue”);

rev.defineDone();

done = 0;

do until (done = 1);

set work.Sales end=done;

format Revenue dollar9.;

if rev.find(key: Name) NE 0

then call missing(Revenue);

Revenue = sum(Revenue, Price);

rev.replace();

end;

rev.output(dataset: “work.Revenue”);

run;

Item Sold Price Name

iPhone 7 $800 Malcolm

iPad Air $700 Sean

MacBook $900 Sean

iPad Mini $500 Malcolm

Sales Table

Name Revenue

Malcolm $1,300

Sean $1,800

New Revenue Table

THANKS!

36

Documents

Hash-Object Programming in SAS...Hash-Object Programming in SAS Malcolm MacRae, AESO Sean McCarthy, ENMAX 0. INTRODUCTION TO HASH OBJECTS Malcolm MacRae 1. Introduction to Hash Objects