## Featured Articles

#### Basic Math & Pre-Algebra

### 1,001 Basic Math & Pre-Algebra Practice Problems For Dummies

To successfully master basic math, you need to practice addition, subtraction, multiplication, and division problems. You also need to understand order of operations, fractions, decimals, percents, ratios, weights and measures, and even a little geometry. [more…]

#### Basic Math & Pre-Algebra

### How to Find the Least Common Multiple

The least common multiple (LCM) of a set of numbers is the lowest positive number that is a multiple of every number in that set. This article shows you how to find the LCM. [more…]

## Most Recent

#### R

### How to Create a Data Frame from a Matrix in R

You can create a data frame from a matrix in R. Take a look at the number of baskets scored by Granny and her friend Geraldine. If you create a matrix [more…]

#### R

### Naming Observations in R

One important difference between a matrix and a data frame in R is that data frames always have named observations. Whereas the rownames() function returns [more…]

#### R

### How to Extract Variables, Observations, and Values from a Data Frame in R

In many cases, you can extract values from a data frame in R by pretending that it’s a matrix. But although data frames may look like matrices, they definitely are not. Unlike matrices and arrays, data [more…]

#### R

### How to Add Observations to a Data Frame in R

As time goes by, new data may appear and needs to be added to the dataset in R. Just like matrices, data frames can be appended using the rbind() function. [more…]

#### R

### How to Add Variables to a Data Frame in R

A data frame can be extended with new variables in R. You may, for example, get data from another player on Granny’s team. Or you may want to calculate a new variable from the other variables in the dataset [more…]