To account for experimental error, always fit a smooth curve to the data, using your best judgment as to whether or not the data are continuous. Reversed axes Extrapolation Extrapolation of data refers to continuing a curve fit beyond the range of the actual data set. It is always safe to keep the curve fit within the data range and let the reader decide if and how the curve could be extrapolated. If you carry a curve fit beyond the limits of the data you are assuming that the relationship holds for the independent variables in that range. Sometimes that assumption turns out to be ludicrous.
Extrapolation refers to curvefitting toward the origin as well.
Sometimes extrapolation to the origin is appropriate. Sometimes it is definitely inappropriate. Sometimes a graph is inappropriate Interpolation Interpolation of data refers to the fitting of a continuous curve to a set of data points. It is often necessary to interpolate in order for the figure to clearly show the relationship. When interpolating, care must be taken to avoid bias.