Correlation Graph produces a two variable correlation (how one variable affects another variable) scatter plot.  For example, a correlation graph can show how your flow is affected by rainfall.

FIELDS:

Start Date:  Sets the start date for the graph.

End Date: Sets the end date for the graph.

Graph Title: The main heading for the graph, appears at the top of the graph.

2nd Title: The subheading for the graph.  Appears just below the Graph Title. 

Independent Variable (X):  Use the variable picker to choose the independent variable (shown on the x-Axis).  The cause is the independent variable that affects the dependent variable.  For example, when it rains the plant flow increases.  Rainfall is the independent variable and plant flow is the dependent variable.  Note: The Indepdent Variable and Dependent variable must be of the same frequency for a correlation to be calculated, i.e. they must both be daily, or both be hourly, etc...

Dependent Variable (Y):  Use the variable picker to choose the dependent variable (shown on the Y-Axis).  The cause is the independent variable that affects the dependent variable.  For example, when it rains the plant flow increases.  Rainfall is the independent variable and plant flow is the dependent variable.

Lower Limit: Used to filter the data.  During analysis, any values less than the lower limit are ignored.  If the field is left blank, None displays in the field indicating there is no Lower Limit.

Upper Limit: Used to filter the data.  During analysis, any values greater than the upper limit are ignored.  If the field is left blank, None displays in the field indicating there is no Upper Limit.

Offset: Indicates the forward difference in slots for the variable type (i.e. number of days for daily variables, number of hours for hourly variables, etc...) to be used when comparing a value for the independent variable with that of the dependent variable.  For example, with daily variables, if the offset is 3 (three) the independent value of January 22, 2012 would be compared with the dependent value of January 25, 2012.  Using the Offset, you can do analyses like how yesterday's Rainfall affects todays flow.  Leave blank for no offset.

Correlation Statistics: Four curve fits are calculated; linear, geometric, exponential, and third-order polynomial.  The correlation coefficients are calculated for each curve fit and are a measurement of the goodness of fit.  The higher the Coefficient, the better the fit (1.0 being a perfect fit).  A Linear fit is used as a default.  To select a curve fit to place on the graph, click the plot option button  beside the desired curve fit.

 

BUTTONS:

	Used to set the date range for the graph.
	Loads a previously saved graph defination.
	Displays the graph based on the current settings on the View Correlation form.
	Closes the form.

EXAMPLES:

Graph showing how rainfall affects your flow, linear curve fit choosen: