*Stata programming by Example
*Tutorial 4
**Looking at the if statement


*--------------Start Example  1 ----------------*

sysuse auto, clear

forvalues i=1/22 {

if `i'<5 {
display as text "`i' is a number less than 5"
}
}

*--------------End Example----------------------*



*--------------Start Example  2 ----------------*

sysuse auto, clear

forvalues i=1/22 {

if `i'<5 {
display "`i' is a number less than 5"
}
else {
display "`i' is a number equal to or greater than 5"
}
}

*--------------End Example----------------------*



*--------------Start Example  3 ----------------*

sysuse auto, clear

forvalues i=1/22 {

if `i'<5 {
display "`i' is a number less than 5"
}

else if `i'==5{
display "`i' is a number equal to 5"
}
else {
display "`i' is a number less than or greater than 5"
}
}

*--------------End Example----------------------*


*The following will probably produce a result that you do not expect!
*--------------Start Example  4 ----------------*

sysuse auto, clear

if mpg==25 {
display "mgp equals 25"
}

tab mpg

*--------------End Example----------------------*
*the table indicates that there are 5 cases where mpg equals 25
*However, none are indicated as the if statement only looks at the 
*first observation



*If you wanted to look at every observation
*--------------Start Example  5 ----------------*

sysuse auto, clear
forvalues i=1/`=_N' {
if mpg[`i']==25 {
display "mgp equals 25"
}
}

tab mpg

*--------------End Example----------------------*


*If you wanted to look at every observation
*--------------Start Example  6 ----------------*
local a=1
sysuse auto, clear
forvalues i=1/`=_N' {
if mpg[`i']==25 {
display "mgp equals 25  case `a' "
local a=`a'+1
}
}

tab mpg

*--------------End Example----------------------*





*End tutorial 4 - programming Stata