How to use the FORECAST.LINEAR function
What is the FORECAST.LINEAR function?
The FORECAST.LINEAR function calculates a value based on existing x and y values using linear regression. Use this function to predict linear trends.
FORECAST.LINEAR replaced the FORECAST function in Excel 2016.
When to predict linear trends?
The data shows an approximately linear relationship between the variables. A scatterplot can be used to visualize this.
The FORECAST.LINEAR function is great for extrapolating a trend beyond the observed data. A linear equation provides a simple method for predicting linear trends.
What is a linear equation?
A linear equation is a type of equation that can be written in the form ax + b = 0, where a and b are constants and x is a variable. A linear equation represents a relationship between two quantities that are proportional to each other.
For example, if you have a linear equation that says y = 3x + 4, it means that for every unit increase in x, the value of y increases by 3 units and when x is zero y is 4.
The graph of a linear equation is always a straight line, a linear equation does not involve powers of variables.
Related functions to linear trends
| Function | Description |
|---|---|
| LINEST(known_y's, [known_x's], [const], [stats]) | Returns statistics for a linear trendline fit to data |
| GROWTH(known_y's, [known_x's], [new_x's], [const]) | Returns predicted y-values for exponential growth trend |
FORECAST.LINEAR Function Syntax
FORECAST.LINEAR(x, known_y's, known_x's)
FORECAST.LINEAR Function Arguments
| x | Required. The data point for which you want to predict a value. |
| known_y's | Required. Known y points. |
| known_x's | Required. Known x points. |
FORECAST.LINEAR function example
Formula in cell D3:
The chart below shows the predicted value as a red dot, based on x and y values represented by the blue line.
FORECAST.LINEAR function not working
FORECAST.LINEAR function returns a
- #VALUE error if x is not numeric.
- #N/A error if known_y's or known_x's is left out.
- #DIV/0! error value if the variance of known_x's evaluates to zero.
What is the formula behind the FORECAST.LINEAR function
a = ȳ - bx̄
b = Σ(x - x̄)(y - ȳ)/Σ(x - x̄)2
x̄ - sample mean
ȳ - sample mean
Functions in 'Statistical' category
The FORECAST.LINEAR function function is one of many functions in the 'Statistical' category.
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