Plots: absolute position of axis endpoints?

As I understand, the size attribute fixes the physical size of the canvas. (Sorry I don’t know the proper terminology.) But, I wonder how to fix the physical positions of the endpoints of the axes.

I’m producing a set of line graphs for which the horizontal axis is exactly the same but the vertical axis differs from figure to figure:

  using Plots
  savefig(plot(xs, ys1; size = . . . ), "figure1.pdf")
  savefig(plot(xs, ys2; size = . . . ), "figure2.pdf")
  # . . .

Because the labels on the vertical axis differs from figure to figure, the physical length of the x axis varies from figure to figure. How can one fix the physical length of the x axis? I don’t mind there is spurious space near the left edge of the figure.

Using the pgfplotsx backend you might get what you are looking for.
Compare: Outer legend positions · Plots and Outer legend positions · Plots

I wonder what usage you have mind of the example in Outer legend positions · Plots . . .

In the example, the length of the x axis changes in the left and right columns because the horizontal size of the legend changes. In the middle column, the length of the x axis is fixed only because there are no elements to the left or right of the y axes.

What I need is to fix the length of the x axis regardless of what exists to the left or right of the plotting area.

And thats how the pgfplotsx-backend behaves (as can be seen in Outer legend positions · Plots), no?