no but bar graphs do have to start at zero
line graphs show a change over time
yes a graph has to start from a point 0.
No. And for examples where they don't look at graphs where the x-axis is years. If the scales do not start at zero, this fact should be clearly indicated.
A bar graph's data doesn't always start with zero but the scale on the y axis should. If you are not going to start the scale with zero then you have to put a squiggly line at the bottom to show that you skipped this space.
have no zero point
If scales are too big, the right picture to represent an item displayed on a graph is not used, or if the graph doesn't start on zero, all are ways the data can be misrepresented!
All graphs are graphical graphs because if they were not graphical graphs they would not be graphs!
Because not all equations have the co-ordinates 0,0 in their data range.