actually i've to do some statistics (maximum,minimum,mean,standard
deviation,....) of a file of data in which each column is a particular
type of data. (the file is a tab separated value).
I was trying to do this by using python (usually i work with fortran or
bash, but i'm learning python), that the reason why i tried to use numpy.
Fredrik Lundh wrote:
<div class="moz-text-flowed" style="font-family: -moz-fixed">maurizio
wrote:
>i tryed to use the module max of numpy,
the problem is that i don't know how to put the column of the file in
an array.
(i'm new in phyton).
anyway if you think there is a better way.....
What kind of file is it? Did you pick numpy because you want to do
matrix operations (beyond just finding a maximum value), or was it
just the first thing you stumbled upon when researching the problem?
A simple pattern for finding the maximum value in a file, using only
plain Python code, is:
max_value = ... some very small value ...
for line in file:
value = ... extract value from line ...
if value max_value:
max_value = value
If it's not obvious what "some very small value" is, given the range
of data you're working with, you can do
max_value = None
for line in file:
value = ... extract value from line ...
if max_value is None or value max_value:
max_value = value
instead (this leaves max_value set to None if the file is empty)
A more experienced Python hacker might write
def get_all_values(file):
for line in file:
value = ... extract value from line ...
yield value
...
max_value = max(get_all_values(file))
instead. But this still leaves us with the problem of extracting the
value. The best way to do that depends on the kind of files you're
working with; for fixed-format text files, you could use string
slicing and int/float for conversion (e.g. "value =
float(line[10:20])", see the tutorial for details); for other text
formats, you could use split/partition or regular expressions, or
maybe an existing module (such as "csv"); for binary formats, there's
a large
number of existing tools.
And if you really want to use numpy for other reasons than just
getting a maximum value from a column, there's plenty of stuff in
NumPy and SciPy (http://www.scipy.org/) that might be useful.
So, in other words, I guess we still need more info.
</F>
</div>
