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# How to Predict a Single Value Using a Regression Model in R

To fit a linear regression model in R, we can use the lm() function, which uses the following syntax:

`model `

We can then use the following syntax to use the model to predict a single value:

`predict(model, newdata = new)`

The following examples show how to predict a single value using fitted regression models in R.

### Example 1: Predict Using a Simple Linear Regression Model

The following code shows how to fit a simple linear regression model in R:

```#create data
df frame(x=c(3, 4, 4, 5, 5, 6, 7, 8, 11, 12),
y=c(22, 24, 24, 25, 25, 27, 29, 31, 32, 36))

#fit simple linear regression model
model ```

And we can use the following code to predict the response value for a new observation:

```#define new observation
new frame(x=c(5))

#use the fitted model to predict the value for the new observation
predict(model, newdata = new)

1
25.36364
```

The model predicts that this new observation will have a response value of 25.36364.

### Example 2: Predict Using a Multiple Linear Regression Model

The following code shows how to fit a multiple linear regression model in R:

```#create data
df frame(x1=c(3, 4, 4, 5, 5, 6, 7, 8, 11, 12),
x2=c(6, 6, 7, 7, 8, 9, 11, 13, 14, 14),
y=c(22, 24, 24, 25, 25, 27, 29, 31, 32, 36))

#fit multiple linear regression model
model ```

And we can use the following code to predict the response value for a new observation:

```#define new observation
new #use the fitted model to predict the value for the new observation
predict(model, newdata = new)

1
26.17073
```

The model predicts that this new observation will have a response value of 26.17073.

### Potential Errors with Predicting New Values

The most common error you may run into when attempting to predict a new value is when the dataset you used to fit the regression model does not have the same column names as the new observation youâ€™re attempting to predict.

For example, suppose we fit the following multiple linear regression model in R:

```#create data
df frame(x1=c(3, 4, 4, 5, 5, 6, 7, 8, 11, 12),
x2=c(6, 6, 7, 7, 8, 9, 11, 13, 14, 14),
y=c(22, 24, 24, 25, 25, 27, 29, 31, 32, 36))

#fit multiple linear regression model
model ```

Then suppose we attempt to use the model to predict the response value for this new observation:

```#define new observation
new #use the fitted model to predict the value for the new observation
predict(model, newdata = new)