## Functions for data aggregation

Aggregation is a term that signifies unification and calculation. It combines one or more data sets, which are given as function arguments, for performing a mathematical operation. This may be: summing up a series of data, counting, averaging, calculating the minimum or maximum value of a given set of numbers… Aggregate functions are very commonly used and should know them well.

## The richness of functions

Excel has a large number of functions, organized according to categories (mathematical, statistical, logical, informative, financial, functions for working with text, etc.). When we start typing the formula and choosing the desired function it automatically displays the syntax in the form of a tooltip that facilitates the input of the function arguments. We can also add functions by selecting a window to insert functions that will be further discussed in the text that follows …

## How Excel calculates?

How Excel calculates is seldom asked question, because we perceive this operation as something that is implicit. After all, how much can drive a car while never knowing how’s the engine running ? However, there is a situation where the calculation method can be very important: when the data is downloaded from external sources or when we perform complex calculations of the ones that are important to use the full power of the CPU.

## Error bars

Sometimes the chart will show values ​​that are not reliable. In that case, it would be good to emphasize to the observer that the error exists, and how its tolerance is. For this purpose, error lines are used that express a potential error, relative to the point or marker for the given data set. They can also be used to highlight some future trends, or to make assumptions about future value data.

## Trend line

Charts are often expected to present the current state and projection of future events. Nobody reliably knows what will happen in the future, but by approximating past data, it is possible to identify trends. Trend, by definition, represents the general direction of development or change. Excel sets trends and displays them using the trend line by application of  various mathematical functions.