This tutorial explains how to use PROC FREQ with various examples. The PROC FREQ is one of the most frequently used SAS procedures which helps to summarize categorical variable. It calculates count/frequency and cumulative frequency of categories of a categorical variable. In other words, it returns the number and percentage of cases falling in multiple categories of a categorical variable. It's not just restricted to counts. It also produces bar charts and tests for association between two categorical variables.
Create a sample data setThe program below creates a sample SAS dataset which would be used in further examples to explain PROC FREQ.
data example1;The created dataset looks like below -
input x y $ z;
cards;
6 A 60
6 A 70
2 A 100
2 B 10
3 B 67
2 C 81
3 C 63
5 C 55
;
run;
X | Y | Z |
---|---|---|
6 | A | 60 |
6 | A | 70 |
2 | A | 100 |
2 | B | 10 |
3 | B | 67 |
2 | C | 81 |
3 | C | 63 |
5 | C | 55 |
Example 1 : To check the distribution of a categorical variable (Character)
Suppose you want to see the frequency distribution of variable 'y'.
proc freq data = example1;The TABLES statements tells SAS to return n-way frequency and crosstabulation tables and computes the statistics for these tables.
tables y;
run;
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Output : PROC FREQ |
It answers a question 'which category holds the maximum number of cases'. In this case, the category 'C' contains maximum number of values.
Tip :
Categorical variables are of two types - Nominal and Ordinal. A nominal variable is a categorical variable in which categories do not have any order. For example, gender, city etc. An ordinal categorical variable has categories that can be ordered in a meaningful way. For example, rank, status (high/medium/low) etc.
Example 2 : To remove unwanted statistics in the table
proc freq data = example1;
tables y /nocum;
run;
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NOCUM Option |
If you want only frequency, not percent distribution and cumulative statistics.
proc freq data = example1;
tables y /nopercent nocum;
run;
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NOPERCENT and NOCUM option |
Example 3 : Cross Tabulation ( 2*2 Table)
proc freq data = example1;
tables y * x;
run;
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Proc Freq Output |
Example 4 : Show Table in List Form
Suppose you do not want output to be shown in tabular form. Instead, you want final analysis to be displayed in list form (See the image below)
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PROC FREQ List Form |
proc freq data = example1;The forward slash followed by LIST keyword produces the list styled table.
tables y * x / list;
run;
Example 5 : Hide Unwanted Statistics in Cross Tabulation
The NOROW option hides row percentage in cross tabulation. Similarly, NOCOL option suppresses column percentage.
proc freq data = example1;
tables y * x / norow nocol nopercent;
run;
The NOROW option hides row percentage in cross tabulation. Similarly, NOCOL option suppresses column percentage.
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NOROW and NOCOL Options |
Example 6 : Request Multiple Tables
Suppose you want to generate multiple crosstabs. To accomplish it, you can run the command below-
Example 7 : Number of Distinct Values
The NLEVELS option is used to count number of unique values in a variable.
Example 8 : Use WEIGHT Statement
The WEIGHT statement is used when we already have the counts. It makes PROC FREQ use count data to produce frequency and crosstabulation tables.
Suppose you want to generate multiple crosstabs. To accomplish it, you can run the command below-
proc freq data = example1;
tables y * (x z) / norow nocol nopercent;
run;
The tables y*(x z) statement is equivalent to tables y*x y*z statement. In this case, it returns two tables - y by x and y by z.Example - tables (a b)*(c d); is equivalent to tables a*c b*c a*d b*d;
Example 7 : Number of Distinct Values
The NLEVELS option is used to count number of unique values in a variable.
proc freq data = example1 nlevels;
tables y;
run;
In this case, it returns 3 for variable Y.
Example 8 : Use WEIGHT Statement
Data example2;
input pre $ post $ count;
cards;
Yes Yes 30
Yes No 10
No Yes 40
No No 20
;
run;
proc freq data=example2;
tables pre*post;
weight count;run;
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PROC FREQ Weight Statement |
Example 9 : Store result in a SAS dataset
Suppose you wish to save the result in a SAS dataset instead of printing it in result window.
proc freq data = example1 noprint;The OUT option is used to store result in a data file. NOPRINT option prevents SAS to print it in results window.
tables y *x / out = temp;
run;
Example 10 : Run Chi-Square Analysis
proc freq data = example1 noprint;Example 11 : Generate Bar Chart and Dot Plot
tables y * x/chisq;
output All out=temp_chi chisq;
run;
The bar chart can be generated with PROC FREQ. To produce a bar chart for variable 'y', the plots=freqplot (type=bar) option is added. By default, it shows frequency in graph. In order to show percent, you need to add scale=percent. The ODS graphics ON statement tells SAS to produce graphs. Later we turn it off.
Ods graphics on;Proc freq data=example1 order=freq;
Tables y/ plots=freqplot (type=bar scale=percent);
Run;
Ods graphics off;
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Bar Chart with PROC FREQ |
Similarly, we can produce dot plot by adding type=dot. See the implementation below-
Ods graphics on;
Proc freq data=example1 order=freq;
Tables y/ plots=freqplot (type=dot);
Run;
Ods graphics off;
Example 12 : Include Missing Values in Calculation
By default, PROC FREQ does not consider missing values while calculating percent and cumulative percent. The number of missing values are shown separately (below the table). Refer the image below.
Proc freq data=sashelp.heart;
Tables deathcause;
Run;
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Exclude Missing : Proc FREQ |
Proc freq data=sashelp.heart;
Tables deathcause / missing;
Run;
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Include Missing : PROC FREQ |
Example 13 : Ordering / Sorting
In PROC FREQ, the categories of a character variable are ordered alphabetically by default. For numeric variables, the categories are ordered from smallest to largest value.
To sort categories on descending order by frequency (from largest to smallest count), add ORDER=FREQ option
Proc freq data=sashelp.heart order = FREQ;It is generally advisable to show distribution of a nominal variable after sorting categories by frequency. For ordinal variable, it should be shown based on level of categories.
Tables deathcause / missing;
Run;
To order categories based on a particular FORMAT, you can use order = FORMATTED option.
Conclusion
PROC FREQ is a simple but powerful SAS procedure. This tutorial was designed for beginners who have no background of any programming language. Hope the above examples help to understand the procedure crystal clear.
Good explaination!
ReplyDeleteThank you!
DeleteGreat tutorial...
ReplyDeletecould you also explain more on 'WEIGHT statement'
yes youre right? even i do not understand this syntax called 'weight';
DeleteGood work, Keep it up :)
ReplyDeleteGlad you liked it. Cheers!
DeleteGood question bank and explanations.Keep posting!!
DeleteSimply amazing...
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ReplyDeleteGood Work, luck to stumble upon your site.
ReplyDeleteAmazing tutorial. Keep up the good work!
ReplyDeleteAmazing description. You are really making it easy for SAS beginners :)
ReplyDeleteThank you for your effort and resources
how to use by statement in proc freq
ReplyDeleteBest...I learned alot
ReplyDeletethanks sir
ReplyDeleteGood presentation sir
ReplyDeleteHi Deepanshu,
ReplyDeleteWell explained. I have 1 query regarding ods file. We are using VM space and when we are trying to save the following error occured. Could you please help.
ods rtf file = "C:\Users\kiran\table1a.rtf" style = forNESUG;
WARNING: Style FORNESUG not found; Rtf style will be used instead.
ERROR: Insufficient authorization to access /opt/sasinside/SASConfig/Lev1/SASApp/C:\Users\kiran\table1a.rtf.
Excellent explanations. Really easy to understand SAS programming through your portal.
ReplyDeleteExcellent explanations. Really easy to understand SAS programming through your portal.
ReplyDeleteThanks
ReplyDeleteVery good!!
ReplyDeleteExcellent explanations. You make me the life easier.
ReplyDeleteThis comment has been removed by the author.
ReplyDeleteThat is a very nice and well explained summary, thank you!
ReplyDeletethanks for excellent turorials. copy and pasted your code but not working..
ReplyDeleteproc freq data = example1 noprint;
tables y * x/chisq;
output All out=temp_chi chisq;
run;
Fantastic! Every one of the tutorials worked for me.
ReplyDeleteThank you very much.
Charles
Glad you found it helpful. Cheers!
DeleteThank you for you explanation. Very nice of you!
ReplyDeleteGreat, thanks
ReplyDeleteExellent explanation ! Thank You so much!
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ReplyDeleteThank you so very much!!
Good work 👍
ReplyDeletewrite a program to get output using proc freq
ReplyDeleteX1 X2
N 19
M 10
F 9
write a program to get output using proc freq
ReplyDeleteX1 X2
N 19
M 10
F 9
Ans: I think we can create a new data set and run the proc freq. I pasted the code below I hope this is what you expecting please let me know.
data temp;
input x1 :$10. x2;
datalines;
N 19
M 10
F 9
;
run;
proc freq data= temp;
run;