High Quality Content by WIKIPEDIA articles! High Quality Content by WIKIPEDIA articles! In science and engineering, a semi-log graph or semi-log plot is a way of visualizing data that are changing with an exponential relationship. One axis is plotted on a logarithmic scale. This kind of plot is useful when one of the variables being plotted covers a large range of values and the other has only a restricted range the advantage being that it can bring out features in the data that would not easily be seen if both variables had been plotted linearly.