I have a graphics object stored in variable g1 that was generated using ListLinePlot. It consists of data imported from a csv file and has some options setting like PlotRange, TicksStyle, AxesStyle and ImageSize.
Now I want to add some graphics primitives to it such as lines and rectangles.
So what I tried was
Show [ { g1, Graphics[{some primitives}] } ]
But nothing shows up. I tried it on a more simple plot - Plot[Sin[x],{x,-1,1}] - and I did manage to see the lines and rectangles.
I am also aware of the “down direction is minus y coordinate” issue.
Is there something I am missing here? Perhaps something about layers and object over object precedence?
The circle is there, but it is outside the range of the Plot, as you will realize if you replace Circle with Disk. To make the circle visible, add the option PlotRange -> All to Show, otherwise it will honour the PlotRange of the first object. This is a venerable old pitfall of Mathematica.
Mistake for me. I gave different names for the horizontal ticks and vertical ticks. The horizontal span in my g1 plot is actually from 1.14 10^-2 sec to 1.16*10^-2 sec (and not from 11.4 sec to 11.6 sec), therefore drawing a circle with its center at {1,1} compresses the whole information to a short horizontal band. Same manipulation was made to the vertical axis.
Therfore, I am going to use the ImageScale function to draw my lines, rectangles and circles, it solves the problem.