Creating a Scattergram (X,Y) Plot for Two Variables

RockWorks | Utilities | Statistics | Scattergram

This program is used to plot the data listed within a designated column in the datasheet against the data within another column. A variety of interpolation techniques are available. 

Menu Options
Step-by-Step Summary

Menu Options

• Input columns: Use these prompts along the left side of the window to select the column of values in the datasheet to be plotted along the axes of the scatter plot. 
  • X: Select the column in the main data window that contains the data to be plotted along the X (horizontal) axis of the XY plot.
  • Y: Select the column in the main data window that contains the data to be plotted along the Y (vertical) axis of the XY plot.
  • Tip: If you want the X-axis of the scatter plot to represent time, be sure to translate standard dates (such as "2/1/1999") to decimal stardates ("1999.08606") using the Dates -> Stardates command in the Coords menu.
     
• Symbols: This box, in the middle pane of the window, should be checked so that symbols will be displayed in the scatter plot. Expand this item to establish the symbol settings. You can choose from fixed symbols, or use symbols listed in the datasheet. (These settings are shared by all of the symbol-plotting routines in the program; click here for more information.)
   
• Labels: Insert a check here if you want the individual symbols to be labeled with text of your choice (for example, ID). Expand this item to set the label options. (Like the symbols, these settings are shared by all of the symbol-label-plotting routines in RockWorks; click here for more information.)
  DON’T turn labels on if you have a lot of points or the plot will be unreadable. 
   
• Scaling: Expand this item to set the axis scaling:
  • X Axis: Choose Linear or Logarithmic scaling for the X axis.
  • Y Axis: Choose Linear or Logarithmic scaling for the Y axis.
     
• Connect Points: Insert a check in this box to activate the plotting of a line between scattergram points. This is typically used with data plotted in a sequential fashion over time along the X axis. Expand this item to select line style and color.
   
• Smooth Curve Fit: Insert a check in this setting to activate the plotting of a smoothed line between data points. This is a point-to-point line, not a polynomial curve fit to the data points. Expand this item to access settings. 
  • Smoothing Factor: The program can smooth the curves in one or more passes resulting in more pleasant-looking lines. However, smoothed lines may not always honor the original points. Click on this item to enter the number of times the lines should be run through the "smoother".
  • Style/Color: Select the line style, color, and thickness for the curve. 
     
• Linear Regression: Insert a check here to illustrate the linear "relatedness" of the X and Y variables by plotting the best-fit line among the data points and by reporting relatedness in terms of the correlation coefficient. Expand this item to access settings. 
  • Show Correlation Coefficient: Insert a check here for the program to display a small window prior to plotting the scattergram that lists the computed correlation coefficient for the selected columns. 
    The correlation coefficient ranges from -1 to + 1. A value of 1.0 indicates a perfect direct relationship between the variables. A correlation coefficient of 0.5 indicates that there is some relationship, and a correlation of 0 indicates no relationship at all between the two variables.
    Negative correlation coefficient values indicate one variable is increasing while the other decreases. Like the positive values, a correlation of -1 indicates a perfect, though inverse, relationship, and a correlation of -0.5 reflects a less than perfect inverse relationship.
  • Style/Color: Select the line style, color, and thickness for the regression line. 
     
• Polynomial Fit: Insert a check in this box if you want the program to fit a polynomial equation to the data points and to offer a statistical display. Expand this item to establish the settings. Note: Polynomial fitting is limited to 500 data points. 

  • Order: Click on this item to select the order of the polynomial to be fit to the data.  See the diagrams below for examples of first through third order polynomials.  You may select a fourth or fifth order polynomial (with 3 or 4 bends, respectively), but you probably won't want to go higher than that since few natural phenomena are truly higher order occurrences. RockWorks will, however, permit up to 10 orders. 

  
   

  • Show Equation & Std Dev.: Insert a check in this box to display the computed standard deviation and polynomial equation prior to creating the diagram.
  • Style/Color: Select the line style, color, and thickness for the regression line. 
     
• Border Annotation: Insert a check here to activate the plotting of titles, ticks, and labels along the horizontal and vertical axes. Expand this item to access the settings. 
  • Left/West Axis, Right/East Axis, Basal/South, Top/North Axis: Insert a check in any of these check-boxes to activate their plotting. Expand each item to access common settings: 
    • Ticks: To turn tick marks on for any activated axis, insert a check in the appropriate check-box. Expand the Ticks to set size (as a percent of the diagram width) and color. 
    • Labels: To turn labeling on for any activated axis, place a check in the appropriate check-box. Expand this heading to set label angle, size (as a percent of the diagram width), color, and font type.  
    • Titles: To turn titles on for any activated axis, place a check in the appropriate check-box. Expand Titles to enter the text to be plotted for the title, and to set label angle, size (as a percent of the diagram width), color, and font type.
    • Subdividers: Expand this to turn on/off the plotting of a horizontal and/or vertical grid of lines, at major and minor intervals. Once activated, expand the items to choose the colors and line styles for the selected grids. 
       
• Manual Ranges: Insert a check in this box if you want to establish a range of data for the diagram that is either less than the actual data values (to filter the data), or greater than the actual data values (to extend the axes for comparing different data sets).  If the Manual Ranges check-box is left blank, the program will use all scanned data and dimension the X and Y axes to accommodate those data.  Expand this item to enter the desired ranges.  
  • X Minimum, X Maximum: Click on these items to type in the minimum and maximum data values to be represented for the variable selected for the X axis. 
  • Y Minimum, Y Maximum: Click on these items to type in the minimum and maximum data values to be represented for the variable selected for the Y axis.
     
• Manual Subdivision: Insert a check here to override the program-computed axis labeling intervals. Expand this item to access settings. 
  • X Minor: Type in the interval for the X axis at which small tick marks are to be plotted. 
  • X Major: Enter the X axis interval at which major tick marks and labels are to be plotted. This must be an even multiple of the X Minor setting. 
  • Y Minor: Type in the interval for the Y axis at which small tick marks are to be plotted. 
  • Y Major: Enter the Y axis interval at which major tick marks and labels are to be plotted. This must be an even multiple of the Y Minor setting. 
     
• Diagram Dimensions: Expand this item to enter the height and width of the diagram. These values would typically represent inches, however note that you can scale the diagram both larger and smaller for both screen display and printer output in the RockPlot2D plotting window. 
  
  

Step-by-Step Summary

1. Access the RockWorks Utilities program tab. 
2. Enter/open/import your data to be analyzed into the datasheet. 
3. Select the Statistics | Scattergram menu option. 
4. In the displayed dialog box enter the requested information, discussed above. 
5. Click Process to continue.
   
   The program will generate the scattergram and display it in a RockPlot2D tab.
   
   
6. You can adjust any of the settings in the Options window and then click the Process button again to regenerate the diagram(s).
   ! Each time you click the Process button, the existing display(s) will be replaced.
   
   
7. View / save / manipulate / print / export the diagram in the RockPlot2D window. 
   
   

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