STAM 102 :: Lecture 09 :: Use of in-built functions and writing expressions
                  
				
In-built Functions
- A function is an in-built program, which is used to do a particular task.
 - Functions take the input the input and will give the result as the output.
 - Based on the input and output data the functions are categorized as
 - String functions
 - Arithmetic functions
 - Date functions
 - Logical functions
 - Group functions
 
Use of in-built function SUM()
To use  in-built functions enter the data to prepare mark list of the I- B.Sc.(Agriculture)  students in the spreadsheet.

- Using the in-built function SUM() we can calculate the total scored by each and every student in I-B. Sc. (Agri.).
 - Add Total column in the spreadsheet as shown below:
 

- Place the mouse pointer in the cell with the address F3
 - The F3 cell is the one which should display the total mark scored by the student namely Angaleeswari in the above example.
 - Click on Insert Menu à Function
 
- or Select fx in the Formula bar
 - Insert Function dialog box will get displayed as shown below:
 

- Select SUM function and click OK button in the Insert Function dialog box.
 - The function Argument dialog box will be displayed with the automatically assumed range of cells to be added(B3 to E3)
 

- Click OK. The result is displayed as shown. We can even choose the range of cells added manually.
 

- The total marks scored by the other students have to added in the same way by making use of the SUM() function.
 - Instead entering the same function for all the students in the example we can copy the formula to the cells in the total column to add B4:E4, B5:E5, B6:E6 and so on.
 - When we copy the SUM() function formula from the cell F3 to F4 the SUM function will automatically taking the input range of numbers to be added is B4:E4.
 - The same is applicable to the rest of the cells in the total column.
 - To copy down the formula place the mouse pointer at the bottom right corner of the cell F3.
 - The mouse pointer now automatically changes into + symbol.
 - Now drag + symbol down the cells in the Total column.
 - We can see the total marks of all the students in the example as shown below.
 

Use of in-built function AVERAGE()
- To calculate the average marks scored by the students in the example we can make use of average function AVERAGE().
 - Enter Average column in the spreadsheet.
 
- Place the mouse pointer in the cell with the address G3
 - The F3 cell is the one which should display the total mark scored by the student namely Angaleeswari in the above example.
 - Click on Insert Menu à Function
 
- or Select fx in the Formula bar
 - Insert Function dialog box will get displayed as shown below. Choose AVERAGE() function and click OK.
 

- Click OK button in the Insert Function dialog box.
 - In the Function Argument dialog box enter F3/4 then click OK button. The average scored is displayed.
 

- Copy the AVERAGE formula as we copied the SUM().
 

                  
Writing Expressions
- The total marks can be calculated by writing expressions.
 - Place the cursor the cell F3.
 - To enter expression, enter the equal sign first.
 

- Choose the cells with the cursor as sown
 

- Press enter. The result will be displayed in F3. Copy the expression down the Total column to find the total mark scored by all the students in the example.
 - To calculate the averages place the G3.
 - Enter the equal sign first in the cell G3.
 - Enter F3/4 which is the average to be calculated.
 

- Press enter. The average will be displayed. Copy the expression down the cells in the Average column to calculate the rest of the averages.
 

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