Trend line refers to a straight or a curved line that is superimposed on the chart to inform user about direction of the data or the trend, and hence helps in predicting the future values. Due to ability to depict future prices, trend lines are often used in trade analysis to understand the price movement and forecast the value of securities.
In FlexChart, trend lines can be implemented by creating an instance of the TrendLine class. Then, you need to bind the trend line to a data source, set other relevant properties and add it to the Series collection. FlexChart supports regression as well as nonregression trend lines and the fit type and order of these lines can be specified using the FitType property and Order property of this class respectively. Following is the list of various fit types supported in the FlexChart control:
TrendLine.FitType  Snapshot  Description 

Linear  A linear trend line is the straight line that most closely approximates the data in the chart. The data is linear, if the data pattern resembles a line. Equation  Y(x) = C0 + C1*x 

Polynomial  Polynomial trend lines are curved lines that are used with fluctuating data. They are useful for analyzing gains or losses over a large data set. When using a polynomial trend line, it is important to also set the Order of the line, which can be determined by the number of fluctuations in the data. Equation  Y(x) = C0 + C1*x + C2*x2 + : + Cn1*xn1 

Logarithmic  Logarithmic trend line is a bestfit curved line that is most useful when the rate of change in the data increases or decreases quickly and then levels out. A logarithmic trend line can use negative and/or positive values. Equation  Y(x) = C0 * ln(C1*x) 

Power  Power trend line is a curved line that is best used with data sets that compare measurements that increase at a specific rate — for example, the acceleration of a race car at onesecond intervals. You cannot create a power trend line if your data contains zero or negative values. Equation  Y(x) = C0 * pow(x, C1) 

Exponent  Exponential trend line is a curved line that is most useful when data values rise or fall at increasingly higher rates. You cannot create an exponential trend line if your data contains zero or negative values. Equation  Y(x) = C0 * exp( C1*x) 

Fourier  Fourier trend line identifies patterns or cycles in a series data set. It removes the effects of trends or other complicating factors from the data set, thereby providing a good estimate of the direction that the data under analysis will take in the future. Equation  Y(x) = C0 + C1 * cos(x) + C2 * sin(x) + C3 * cos(2*x) + C4 * sin(2*x) + ... 

MinX  The minimum Xvalue on the chart.  
MinY  The minimum Yvalue on the chart.  
MaxX  The maximum Xvalue on the chart.  
MaxY  The maximum Yvalue on the chart.  
AverageX  The average Xvalue on the chart.  
AverageY  The average Yvalue on the chart. 