# How to determine the trend of a trend line

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The type of data you have determines the type of trendline you should use.

### Add Trend Lines to a Visualization

Trendline reliability A trendline is most reliable when its R-squared value is at or near 1. When you fit a trendline to your data, Graph automatically calculates its R-squared value.

If you want, you can display this value on your chart. Linear A linear trendline is a best-fit straight line that is used with simple linear data sets.

Your data is linear if the pattern in its data points resembles a line. A linear trendline usually shows that something is increasing or decreasing at a steady rate.

### Choosing the best trendline for your data

In the following example, a linear trendline clearly shows that refrigerator sales have consistently risen over a year period.

Notice that the R-squared value is 0. Logarithmic A logarithmic trendline is a best-fit curved line that is most useful when the rate of change in the data increases or decreases quickly and then levels out.

The following example uses a logarithmic trendline to illustrate predicted population growth of animals in a fixed-space area, where population leveled out as space for the animals decreased. Note that the R-squared value is 0. Polynomial A polynomial trendline is a curved line that is used when data fluctuates.

Additional Resources Trend Lines As technical analysis is built on the assumption that prices trend, the use of trend lines is important for both trend identification and confirmation. A trend line is a straight line that connects two or more price points and then extends into the future to act as a line of support or resistance.

It is useful, for example, for analyzing gains and losses over a large data set. The order of the polynomial can be determined by the number of fluctuations in the data or by how many bends hills and valleys appear in the curve.

An Order 2 polynomial trendline generally has only one hill or valley.

### Identify Trend Lines on Graphs - Expii

Order 3 generally has one or two hills or valleys. Order 4 generally has up to three. The following example shows an Order 2 polynomial trendline one hill to illustrate the relationship between speed and gasoline consumption.

Power A power trendline 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 one-second intervals.

You cannot create a power trendline if your data contains zero or negative values. In the following example, acceleration data is shown by plotting distance in meters by seconds.

The power trendline clearly demonstrates the increasing acceleration. Exponential An exponential trendline is a curved line that is most useful when data values rise or fall at increasingly higher rates.

### Linear trend estimation

You cannot create an exponential trendline if your data contains zero or negative values. In the following example, an exponential trendline is used to illustrate the decreasing amount of carbon 14 in an object as it ages. Note that the R-squared value is 1, which means the line fits the data perfectly. Moving average A moving average trendline smoothes out fluctuations in data to show a pattern or trend more clearly.

Two-way tables Video transcript Shira's math test included a survey question asking how many hours students had spent studying for the test. The graph below shows the relationship between how many hours students spent studying and their score on the test. Shira drew the line below to show the trend in the data. Assuming the line is correct, what does the line slope of 15 mean? So let's see.

A moving average trendline uses a specific number of data points set by the Period optionaverages them, and uses the average value as a point in the trendline. If Period is set to 2, for example, then the average of the first two data points is used as the first point in the moving average trendline.

### How to Determine the Y-Intercept of a Trend Line

The average how to determine the trend of a trend line the second and third data points is used as the second point in the trendline, and so on. In the following example, a moving average trendline shows a pattern in number of homes sold over a week period. Need more help?