It is familiar concept, briefly described for drawing frequency curves. In case of a time series a scatter diagram of the given observations is plotted against time on the horizontal axis and a freehand smooth curve is drawn through the plotted points. The curve is so drawn that most of the points concentrate around the curve, however, smoothness should not be scarified in trying to let the points exactly fall on the curve. It would be better to draw a straight line through the plotted points instead of a curve, if possible. The curve fitted by this method eliminates the short term and long term oscillations and the irregular movements from the time series and elevate the general trend. After having drawn such a curve or line the trend values or the estimated values, which may be denoted by, can be read from the graph corresponding to each time period.
Example: Measure the trend by method of freehand curve from the given data of production of wheat in a particular area of the world.