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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")]
    ]

 0.0820573382679496654`5.937562804821409

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

 44.8033066943005173068`5.937562804821409