# Plotting error message regarding numerical type of function arguments

I am trying to plot the following function:

```
x = var('x')
def y(x): return RR(len(prime_range(floor(0.95 * x), floor(1.25 * x))) / round(1.25 * x - 0.95 * x))
```

I am not sure whether it is well-constructed mathematically, but it's trying to check the density of prime numbers around a given value `x`

I am using the `floor()`

function because I'm not sure that `prime_range()`

accepts non-integers.

If I test the function with random real values of `x`

I get a plausible output without errors.

However, when I try to plot the function as in:

```
plot(y(x), (x, 5, 20))
```

I get the following error message:

```
TypeError: unable to convert floor(0.950000000000000*x) to an integer
and argument is also not real: unable to simplify to float approximation
```

I don't understand why this input cannot be understood as real by sagemath, or why the floor is not an integer.

To find out if

`prime_range`

accepts non-integers, you could just try it and see what happens. Try`prime_range(30.438)`

.Thank you! @John Palmieri