floating_in_text.Rmd

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---

# Formats for floating point values in text files

Let's say we have a floating point numbers like this:

```{python}
a_number = 314.15926
a_number
```

We can also represent these numbers in exponential format.  Exponential format
breaks the number into a two parts: the *significand*; and the *exponent*.

The significand is a floating point number with one digit before a decimal
point.  The exponent is an integer.  For example:

```{python}
exp_number = 3.1415926E2
exp_number
```

Here the significand is `3.1415926`, and the exponent is `2`, the value after
the `E`.  The number is given by `s * 10 ** e` where `s` is the significand and
`e` is the exponent.  In this case: `314.15926 = 3.1415926 * 10 ** 2`.

This exponential format is the default format that `np.savetxt` uses to
represent floating point numbers when writing to text files.  For example:

```{python}
import numpy as np

an_array = np.array([a_number, 1.0, 2.0])
an_array
```

```{python}
# Save the array as a text file.
np.savetxt('some_numbers.txt', an_array)
```

```{python}
# Show the text in the file
from pathlib import Path

pth = Path('some_numbers.txt')

print(pth.read_text())
```

Finally, clean up the temporary file:

```{python}
pth.unlink()
```