These are sometimes called bar charts.

These are a good way of looking at the spread of data and are very easy to draw.

Remember to number your axes evenly just as you would with a normal algebraic graph. Here's an example:

The marks obtained by 30 pupils in a maths test are as follows:

First tally them:

Now draw your frequency diagram:

With grouped data, the bottom axis should be numbered continuously as on a normal graph with the bars covering the group they represent!

Line Graphs are only used for discrete data and are simply a line (instead of a bar) for each data value showing total frequency.

Again, these are done in the same way as Frequency Diagrams but you do not draw the bars.

Instead you put a little cross where the middle of the bar would have been then join all the crosses together. Here's what a Frequency Polygon would look like for the example used in Frequency Diagrams above: