Trendiviiva
Trendiviiva is the Finnish term for a trend line, a graphical device used to reveal the general direction of a data set in a scatter plot or time-series chart. By fitting a line to data points, the trendiviiva summarizes short-term fluctuations and emphasizes long-term movements, helping to identify patterns such as upward or downward trends. The most common form is the simple linear trendiviiva, derived from linear regression, which minimizes the sum of squared residuals between observed values and the line. The equation y = a + b x represents the relationship, where b is the slope indicating the rate of change and a the intercept. Other approaches include moving-average trend lines, exponential smoothing, and polynomial or nonlinear trend lines that can capture curvature in the data.
Trendiviiva is used across disciplines, including finance to assess price trends, economics to illustrate growth, environmental
Limitations include sensitivity to outliers and the assumption of a stable relationship over the chosen interval;