Annoyingly Microsoft Excel keeps plotting two lines instead of one. If Excel plots two lines from your data set instead of one, this can be fixed by changing the data set.
By default, when you select some data to turn into a graph, Excel will plot each column as a line and use the column to the left of the selected data as the scale (axis). This is contrary to what you would expect when you select two columns, as you’d expect the two columns to be plotted against each other producing a single line. Instead you get two lines, one for each column.
To plot a single line on the graph in Excel, select only one column and plot a graph using that. Excel will use the column to the left as the measure to plot the points against.
❗ Still getting two lines instead of one? Make sure you only select one column of data to plot the graph against. Try moving the columns around and selecting different ones until the graph looks the way you want it.