Air Quality Analysis and Reporting

The script begins by dynamically creating a custom SAS^© format (`pct_`) that associates numerical value ranges with colors (from blue to red) to represent 'cold' to 'hot' levels. It then uses PROC SQL to determine the minimum and maximum values of the 'air' variable in the SASHELP.AIR dataset. A subsequent DATA STEP calculates an 'air quality percentage' indicator, normalized against these min/max values. Finally, PROC TABULATE is used with ODS HTML to generate a visual report, where table cells are colored according to the percentage index, providing a clear view of air quality variations over time.

Data Analysis

Type : SASHELP

Data comes from the SASHELP.AIR dataset, an example dataset integrated into SAS.

1 Code Block

DATA STEP

Explanation :
This DATA _NULL_ block dynamically generates a PROC FORMAT procedure. It creates a format named `pct_` that maps numerical values (representing a percentage from 0 to 1) to hexadecimal color codes. Colors gradually vary from blue (cold, low percentage) to red (hot, high percentage). Values outside the defined range receive a default gray color.

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1	* Create a format to display colors ranging from Blue (cold) to Red (hot) ;
2	DATA _null_ ;
3	call execute('proc format fmtlib ; value pct_') ;
4	max=1;
5	maxloop=255 ;
6	DO i=1 to maxloop ;
7	color='cx'\|\|put(i/maxloop255,hex2.)\|\|'00'\|\|put((maxloop-i)/maxloop255,hex2.) ;
8	from=((i-1)/maxloop)*max ;
9	to=(i/maxloop)*max ;
10	call execute(put(from,best.)\|\|'-'\|\|put(to,best.)\|\|'='\|\|quote(color)) ;
11	END ;
12	call execute('.="light gray" other="cxd0d0d0" ; run ;') ;
13	RUN ;

2 Code Block

PROC SQL

Explanation :
Uses PROC SQL to extract the maximum and minimum values of the 'air' variable from the `sashelp.air` dataset. These values are then stored in the macro variables `&max` and `&min`. A macro variable `&range` is calculated to obtain the total range between the minimum and maximum, which will be used to normalize the data later.

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1	* get the maximum value of air ;
2	PROC SQL ;
3	select max(air),min(air) into :max,:min from sashelp.air ;
4	%let range=%sysevalf(&max-&min) ;

3 Code Block

DATA STEP Data

Explanation :
This DATA STEP creates a new temporary dataset named 'air'. It reads the `sashelp.air` dataset, extracts the year and month from the 'date' variable, and then calculates a new 'pct' variable. This 'pct' variable represents the normalized 'air' value, expressed as a percentage above the minimum and within the range defined by `&range`. It quantifies relative air quality.

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1	* express values of air as a percentage of the maximum ;
2	DATA air ;
3	SET sashelp.air ;
4	year=year(date) ;
5	month=month(date) ;
6	* percentage is the level above the minimum ;
7	pct=(air-&min)/&range ;
8	RUN ;

4 Code Block

PROC TABULATE

Explanation :
This block generates an interactive HTML report ('test.html') using ODS HTML and PROC TABULATE. It displays a pivot table of the 'pct' variable (air quality percentage), classified by year and month. The cell style is modified by applying the previously created `pct_` format, which colors the table cell background according to the 'pct' value, from blue (best) to red (worst), for an intuitive visualization of air quality.

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1	* tabulate the results indicating maximum as red, minimum as blue ;
2	ods html file='test.html' ;
3	title 'Air Quality over the years' ;
4	footnote 'Blue (cold) is best, Red (hot) is worst' ;
5	PROC TABULATE DATA=air style={background=pct_.} ;
6	class year month ;
7	var pct ;
8	label pct='Air Quality Percent of worst month' ;
9	TABLE sum=''pctf=percent.,year='Year',month='Month of Year' ;
10	RUN ;
11	ods html close ;

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