The essential function served by local macros is similar to global macros: to store values. However, global macros stay in the memory long after their execution whereas local macros are dropped after the code is executed (when working in do-files). In most cases, we do not need the value beyond a particular chunk of code and so, it is advisable to use local macros. More importantly, global macros can cause conflicts when you are working across multiple do-files. Since we need file paths throughout and across do-files, file paths can be saved in global macros.

Another difference arises in the coding. To create a local macro, we use the local command, to reference it, we use ` '.

A local macro is, therefore, a box that equals an element (i.e., single-valued) or is a list of elements. Lets start with setting up a single-valued local macro, which follows a similar code as for the global macros we set up previously. An example:

local x 7 // setting up a local macro, x that equals 7
di `x'

local y "pepsi" // setting up a local macro, y that equals "pepsi"
di "`y'" // enclosing `y' in "" because it equals a string

To define a local as a list of elements, simply separate the elements with a single space. An example:

local y_multiple "pepsi coke sprite"
di "`y_multiple"

At this stage, y_multiple can be seen both a single-valued local that equals “pepsi coke sprite” or a local containing a list of names: “pepsi”, “coke”, and “sprite”. The latter is useful in for-loops which we will cover shortly. Before this, lets see some examples of how to use locals.

• A silly example of how to use a local inside a string.

local x 7
di "we defined the local macro x to equal `x'"

• Suppose you want to count the mean number of females who got vaccinated in Tamil Nadu. We can do this:

local state "tamil nadu"
summ female_vac if lgd_state_name == "`state'"
// can check the mean

In both examples, Stata sees `' and realizes that we are using a local. It then finds that local and inputs its value in the expression. In the second example, it sees `state' and inputs tamil nadu in the "".