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The GPLOT Procedure |

The procedure produces a variety of two-dimensional graphs including

- simple scatter plots
- overlay plots in which multiple sets of data points
display on one set of axes
- plots against a second vertical axis
- bubble
plots
- logarithmic plots (controlled by the AXIS statement).

In conjunction with the SYMBOL statement the GPLOT procedure can produce join plots, high-low plots, needle plots, and plots with simple or spline-interpolated lines. The SYMBOL statement can also display regression lines on scatter plots.

The GPLOT procedure is useful for

- displaying long series of data, showing trends
and patterns
- interpolating between data points
- extrapolating beyond existing data with the display
of regression lines and confidence limits.

About Plots of Two Variables |

Scatter Plot of Two Variables (GR21N04(a)) shows a simple scatter plot that plots the values of the variable HEIGHT on the vertical axis and the variable WEIGHT on the horizontal axis. By default, the PLOT statement scales the axes to include the maximum and minimum data values and displays a plus sign (+) at each data point. It labels each axis with the name of its variable or an associated label and displays the value of each major tick mark.

*Scatter Plot of Two Variables (GR21N04(a))*

The program for this plot is in Plotting Two Variables. For more information on producing scatter plots, see PLOT Statement.

You can also overlay two or more plots (multiple sets of data points) on a single set of axes and you can apply a variety of interpolation techniques to these plots. See About Interpolation Methods.

About Plots with a Classification Variable |

Plot of Three Variables with Legend (GR21N08(a)) shows multiple line plots that compare yearly temperature trends for three cities. The legend explains the values of the classification variable, CITY.

*Plot of Three Variables with Legend (GR21N08(a))*

By default, plots with a classification variable generate a legend. In the code that generates the plot for Plot of Three Variables with Legend (GR21N08(a)), a SYMBOL statement connects the data points and specifies the plot symbol that is used for each value of the classification variable (CITY). The program for this plot is in Plotting Three Variables. For more information on how to produce plots with a classification variable, see PLOT Statement.

About Bubble Plots |

Bubble Plot (GR21N01) shows a bubble plot in which each bubble represents a category of engineer that is shown on the horizontal axis. The location of each bubble in relation to the vertical axis is determined by the average salary for the category. The size of each bubble represents the number of engineers in the category relative to the total number of engineers in the data.

The program for this plot is in Generating a Simple Bubble Plot. For more information on producing bubble plots, see BUBBLE Statement.

About Plots with Two Vertical Axes |

Plots with two vertical axes have a right vertical axis that can

- display the same variable values as the left axis
- display left axis values in a different
scale
- plot a second dependent (Y) variable, thereby
producing one or more overlay plots.

In Plot with a Right Vertical Axis (GR21N09) the right axis displays the values of the vertical coordinates in a different scale from the scale that is used for the left axis.

*Plot with a Right Vertical Axis (GR21N09)*

The program for this plot is in Plotting with Different Scales of Values. For more information on how to produce plots with a right vertical axis, see PLOT2 Statement and BUBBLE2 Statement.

About Interpolation Methods |

- connect the data points with straight lines
- specify regression analysis to fit a line
to the
points and, optionally, display lines for confidence limits
- connect the data points to the zero line on the
vertical axis
- display the minimum and maximum values of Y at
each X value and mark the mean value, display standard deviations that connect
the data points with lines or bars, generate box plots, or plot high-low-close
stock market data
- specify that a pattern fill the polygon that is
defined by data points
- smooth plot lines with spline interpolation
- use a step function to connect the data
points

SYMBOL Statement describes all interpolation methods.

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