*Tutorial 5

*Learning Mata by example



*Mata  help

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

help mata      //main mata help file from which you can access other help files

help m5_intro   //main help file for m5

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


*mata function
*--------------Start Example  2 ----------------*

clear mata

mata

real scalar  add1(a, b)   //declared type
  {
  return(a+b)
  }

add1(1,2)


b=J(10,1,2)
c=b*add1(1,2)
c

end

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



*mata function
*--------------Start Example  3 ----------------*

clear mata

mata

function  add1(a, b)      //state function the same result as above
  {
  return(a+b)
  }

add1(1,2)


b=J(10,1,2)
c=b*add1(1,2)
c

end

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



*Mata functions
*--------------Start Example  4 ----------------*

clear mata

version 10
 mata :
void  add(real a, real b)
{
c=a+b
st_numscalar("result",c)
st_numscalar("a",a)
st_numscalar("b",b)

}
end

mata: add(3,4)

di "this result of " a "+" b " ="result


*--------------End Example------------------*
help m1_intro   


*--------------Start Example  5 ----------------*

clear mata

version 10
mata:                                  //start of mata function
string matrix fill(string matrix a1)
{
b1="this"\"is"
a1=a1\b1
a1
return(a1)

}
end


mata:b="this"\"is"
mata: a=fill(b)   //

mata: a

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





**require 10 observations to be fill in with the sequence 1 2 3

*--------------Start Example  6 ----------------*

mata
a=(1\2\3)
a

z=10/rows(a)
for (i=1;i<z;i++) {

if (i==1) {
b=a
}

else {
b=b\a
b
}
}

d=a[1::10-rows(b)]
d

e=b\d
e

end

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



*Reproducing a simplified stata egen fill command
**require 10 observations to be fill in
*Now changing this to a function
*--------------Start Example  7 ----------------*

clear mata
set more off

version 10
mata:                                  //start of mata function
void fill(string a1, real obs)
{

a=strtoreal(tokens(a1))'
a

z=obs/rows(a)
for (i=1;i<z;i++) {

if (i==1) {
b=a
}

else {
b=b\a
b
}
}

d=a[1::obs-rows(b)]
d

e=b\d
e
}
end


mata: fill("1 2 3 4", 41)   //feeds input to mata, "1 2 3 4" are the sequence and 41 are the number of rows

mata: fill("1 10", 6) 

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


**end Tutorial 5