Gallery: Overplotting curves (Python)

A plot can contain multiple objects; in this example we show how to add a second curve to a plot and to annotate it with both a line and a label.

Two curves are created - in this case from different blocks in the same data file; the first, from the data block, is displayed as open squares and the second curve, which is from the fit block, is drawn as a solid red line.

Labels are added to the plot axes and title (these labels can include a subset of LaTeX commands), and the plot re-arranged to make all the labels fit into the display area.

Finally, a line and label are added to the plot to label the second curve. In this example a single segment line is used, so only the start and end locations are given in the add_line call. The vertical alignment of the label is adjusted so that it is centered on the line

The info and info_current can be used to find out what objects have been created and which are current:

chips> print info()
Window [win1]
  Frame [frm1]
    Plot [plot1]   (0.25,0.20)  .. (0.90,0.90)
      Border bottom [bx1]  top [bx2]  left [by1]  right [by2]
      X Axis [ax1]
      Y Axis [ay1]
      Curve [crv1]
      Curve [crv2]
      Line [line1]
      Label [lbl1]

chips> print info_current()
Window [win1]
  Frame [frm1]
    Plot [plot1]
      X Axis [ax1]
      Y Axis [ay1]
      Curve [crv2]
      Line [line1]
      Label [lbl1]
    Coord Sys [Data]
    Coord Sys ID [plot1_ax1ay1]

Here we plot the same data as used in the Two curves in the same plot example, but this time we create a rectangular plot and also display error bars on the first curve.

As with other ChIPS objects, windows will be created automatically for you if needed (e.g. by a call to add_curve). In this example we explicitly create the window using add_window so that we can control the window size. We pick a rectangle 6 inches wide and 3 inches high; these sizes refer to the postscript/PDF output size and will only be approximate for the on screen display; the screen size depends on the dot-pitch of your monitor and can be set using the scalewidth and scaleheight window settings when the window is created.

Since a window exists, the first add_curve call will use it instead of creating a new one. Since the Data Model filter selects four columns from the file - namely x, y, dylo, and dyhi - the curve is plotted with asymmetric Y error bars.

Although in this case the window size was explicitly set, print_window can be made to create postscript and PDF plots of a different size by using some or all of the pagesize, pagewidth, pageheight, fittopage, and keepaspect export options.