I just started using R. I am supposed to Calculate a new variable “Vehic_vol” from the sum of “Psgr_Vol” and “Lugg_Vol” and Plot this new variable against “CITY_MPG” for the whole data set but I end up with ‘x’ and ‘y’ lengths differ ERROR! Any thoughts?

Here is what I did:

```
Vehic_vol<-(VehicleData$Psgr_Vol + VehicleData$Lugg_Vol)
plot (VehicleData$Vehic_vol, VehicleData$CITY_MPG)
```

```
Error in xy.coords(x, y, xlabel, ylabel, log) :
'x' and 'y' lengths differ
```

### 2 Answers

From the code you provided, `Vehic_vol`

is not a column of `VehicleData`

. If you enter in

```
VehicleData$Vehic_vol
```

it returns

```
NULL
```

Note that `NULL`

and `VehicleData$CITY_MPG`

have different lengths (use `length()`

to verify that).

Try this instead

```
plot (Vehic_vol, VehicleData$CITY_MPG)
```

or

```
VehicleData$Vehic_vol <- (VehicleData$Psgr_Vol + VehicleData$Lugg_Vol)
plot (VehicleData$Vehic_vol, VehicleData$CITY_MPG)
```

For Example, my dataset,

```
mod.2 <- lm(CEC ~ clay + ExchNa + ExchCa,
data = subs.soil.data)
```

when you write a model like this and want to draw this modela plot,
`plot(mod.2$y, mod.2$fitted.values) `

this is error “Error in xy.coords(x, y, xlabel, ylabel, log) :
‘x’ and ‘y’ lengths differ”

–First, check with length ()

```
length(mod.2$y)
[1] 0
```

As you can see, the dependent variable y is `0`

in length, i.e. it doesn’t exist.

Solution
```
mod.2 <- lm (CEC ~ clay + ExchNa + ExchCa, data = subs.soil.data,
```

We did not define x and y in the previous formula for mod.2, and this is the cause of the error.**y = TRUE, x = TRUE**)

```
plot(mod.2$y, mod.2$fitted.values)
```

```
> length(mod.2$y)
[1] 146
> length(mod.2$fitted.values)
[1] 146
>
```

This problem has now disappeared.