NTB wrote: > Hello, > I'm an R user, who just started with numpy. I'm planning on setting up > a large nutrient database. Here's my question: > > I'm trying to reshape? or manipulate? the following array: > > array [['Food 1', 'Nutrient 1', 0.9], > ['Food 1', 'Nutrient 2', 0.2], > ['Food 2', 'Nutrient 1', 0.55], > ['Food 2', 'Nutrient 2', 0.11]] > > into a new array that looks like this: > > array [['Food 1', 0.9, 0.2], > ['Food 2', 0.55, 0.11]] > > or more simply: > > array [[0.9, 0.2], > [0.55, 0.11]] > > In other words, the data and shape that I need in the first array is the > 3rd column, where the row names are the 1st column and the column names > are the 2nd column. > > I am thinking that I need to use .flat(), maybe with some kind of list > comprehension? I really don't know, and would really appreciate some help. >
Use itertools.groupby() from the itertools module >>> arr = [['Food 1', 'Nutrient 1', 0.9], ... ['Food 1', 'Nutrient 2', 0.2], ... ['Food 2', 'Nutrient 1', 0.55], ... ['Food 2', 'Nutrient 2', 0.11], ... ] >>> grouped = itertools.groupby(arr, lambda x: x[0]) >>> for name, food in grouped: ... print name ... print [nutrient[2] for nutrient in food] ... Food 1 [0.90000000000000002, 0.20000000000000001] Food 2 [0.55000000000000004, 0.11] you may need to sort the array first since groupby only group adjacent enties. The sorted() and list.sort() function accept a key= argument that would be a function/lambda that generates the key to sort with sorted(arr, key=labmda x: x[0]) or arr.sort(key=lambda x: x[0]) _______________________________________________ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
