## Variables

### Set

Variables in Mathematica are simple. Just type a name and give it a value with the equals sign ( = ).

Here we'll set the variable thisIsAVariable

 thisIsAVariable=10

 10


We can suppress the output by ending the line with a semicolon

 thisIsAVariable=10;


(for those interested, the semi colon denotes that this is a CompoundExpression where the return value is Null )

### SetDelayed

A variable can also have a "delayed" value. That is, its value is calculated when requested. Here we'll set the variable randomValuedVariable .

Use colon-equals ( := ) to do this.

 randomValuedVariable:=RandomReal[];


When we ask for its value, the return value will change every time.

 randomValuedVariable

 0.12257688426972924

randomValuedVariable

 0.13807713447085046


### Clear

The value of a variable can be removed via Clear

 Clear[randomValuedVariable]


The variable now has no value

 randomValuedVariable

 randomValuedVariable


### Simple expressions

We can use variables in expressions to store values for us.

For example, let's do a simple ideal gas law computation for the volume occupied by 2 mols of ideal gas at one atmosphere of pressure and 273 K.

We'll use Mathematica's built in constant data to get the value R in L atm / mol K.

 R$gasConstant= QuantityMagnitude[ UnitConvert[Quantity["MolarGasConstant"], "Liters"*"Atmospheres"/("Moles"*"Kelvins")] ]   0.08205733826794966545.937562804821409  Then we can set up our constants:  n$quantityOfGas=2 (*mols*);
P$externalPressure=1(*atm*); T$temperatureOfGas=273 (*K*);


And finally calculate our volume:

 V$volumeOccupied=n$quantityOfGas*R$gasConstant*T$temperatureOfGas/P\$externalPressure

 44.80330669430051730685.937562804821409