How can I draw the thinnest possible line on a Calc graph?

[AHoerner]

I am trying to put 20 years of daily data on the price and volume of a security into a Calc graph. I currently have the default measurement set to mm and the line thickness set to zero, and I understood that the zero setting was supposed to produce a line one pixel wide, but all my lines are much wiser than that – they are maybe three times as wide as the default grid lines. I thought maybe I was seeing several close together lines combining, but there is nowhere in the graph where the the data lines are nearly as narrow as the grid lines, and that remains true even when I stretch the graph out so that it prints on six pages. It is also ignoring my setting the orientation on landscape, but I assume that is an unrelated problem.

In addition, the only line settings I can find are the default settings – I am relatively new to LO and still finding my way around. Are individual line settings maybe overriding the defaults? Is there a way that I can walk through all the graphical formats that apply to a selected chart?

[librebel]

Hello AHoemer,
A Chart in LibreOffice contains many elements that can each be edited separately.

1) Select the line that you want to format, ( the small green line handles become visible )
2a) Choose the main menu item "Format Selection..."
      OR:
2b) Right-click on the selected line, and choose the contextual menu item "Format Data Series..."
3) In the dialog that pops up, select the tab called "Line",
4) There in the editfield called "Width", you can set the line width to 0mm.