To calculate the ratio, by intuition we will use array. Before using array, we need to transpose the data set.

```
proc transpose data=report_visits_h out=report_visits_v prefix=group;
run;
proc print data=report_visits_v ;
title "-----title print of report_visits_v ";
run;
title "";
```

The output is like:

From the output, we should drop the first row:

```
proc sql;
select count(1) into :m_n from report_visits_v;
quit;
%let n_m_n=%eval(&m_n-1);
%let m_pct=%eval(&n_m_n-1);
data report_visits_v;
set report_visits_v;
if _n_>=2;
drop _name_;
run;
proc print data=report_visits_v;
title "------title trans to horizontal";
run;
title "";
```

Then we can calculate the ratio, like (here use group: to list all vars whose name begin with group):

```
```

```
data report_visits_v;
set report_visits_v;
array a1{*} group: ; ** array with dynamic # of dim;
array a2{*} ratio1-ratio6;
do i=1 to dim(a1);
a2{i}=a1{i}/a1{1};
end;
format ratio2-ratio6 6.5;
drop i;
run;
proc print data=report_visits_v width=min;
run;
```

The output is:

Then we transfer it back to horizontal data, that is, each row is for one group.

```
proc transpose data=report_visits_v out=report_visits_h2;
run;
data orig_records;
set report_visits_h2;
if _n_<=6 then output orig_records;
rename _name_=group;
run;
data ratio;
set report_visits_h2;
if _n_>6 then output ratio;
run;
data ratio(drop=_name_);
retain grp_over_grp1;
set ratio;
grp_over_grp1=substr(_name_,6,1);
run;
proc print data=ratio;
title "------title print of ratio";
run;
title "";
```

Now the print of data set ratio is like:

Next we calculate the percentage of ratio changed for each day compared with the sample ratio.(if macro variable n_m_n without %eval, it will not work here since its resolution will be a character and therefore the resolution could not be used as the number of dim or to indicate how many col are there):

```
data pct;
set ratio;
pct_over_sample = '';
array a3{*} col1-col&n_m_n; ** compare with condition without %eval for n_m_n;
array pct{&n_m_n} ; ** array with dim number being a macro variable;
do i=1 to dim(a3);
pct{i}=(a3{i}-a3{1})/a3{1};
end;
format pct2-pct&n_m_n percentn12.6;
keep pct: ;
run;
proc print data=pct;
title "-----title print of percentage change";
run;
```

The output is:

That is what we want.