Semi-log plot
（重定向自Semilogarithmic plot）
![The log-lin type of a semi-log graph, defined by a logarithmic scale on the y-axis, and a linear scale on the x-axis. Plotted lines are: y = 10x (red), y = x (green), y = log(x) (blue).](/Images/godic/202502/10/LogLinScale.svg1656.png")
![The lin-log type of a semi-log graph, defined by a logarithmic scale on the x axis, and a linear scale on the y axis. Plotted lines are: y = 10x (red), y = x (green), y = log(x) (blue).](/Images/godic/202502/10/LinLogScale.svg1656.png")
![Log-lin pressure–temperature phase diagram of water. The Roman numerals indicate various ice phases.](/Images/godic/202502/10/Phase_diagram_of_water.svg1656.png")
![A semi-logarithmic plot of cases and deaths in the 2009 outbreak of influenza A (H1N1). Notice that while the horizontal (time) axis is linear, with the dates evenly spaced, the vertical (cases) axis is logarithmic, with the evenly spaced divisions being labelled with successive powers of two.](/Images/godic/202502/10/Influenza-2009-cases-logarithmic1656.png")
In science and engineering, a semi-log graph or semi-log plot is a way of visualizing data that are related according to 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.