Saving floats to a file

Question

I have calculated the mean values of several lists. Now I would like to save the data to a txt or csv file. Here's my approach:

k=range(8,15)
for i in k:
    q=range(i)
    g=mean(q)    
    print g        
    savetxt('mean_values.txt', g)

But this gives me IndexError: tuple index out of range. I think it's because savetxt needs an array, but g conatins floats. But even when I define an array g_, I end up with the same Error:

k=range(8,15)
for i in k:
    q=range(i)
    g=mean(q)    
    g_=array(g)    
    print g_
    savetxt('mean_values.txt', g_)

Where's the trick?

Solution 1

In your first attempt you are trying to save a numpy.float64 variable, and documentation says that numpy.savetxt expects an array_like object.

In your second attempt you missed the brackets to specify a matrix g_=array([g]), however if you save the txt inside the loop you will be overwriting your output file each time.

I guess this is what you want:

import numpy as np

g = list()
k = range(8,15)
for i in k:
    q = range(i)
    g.append(np.mean(q))

np.savetxt('myfile.txt', np.array(g), fmt='%.2f')

Output of myfile.txt:

3.50
4.00
4.50
5.00
5.50
6.00
6.50

Solution 2

myFile = open("mean_values.csv","w")
myFile.write("ID" + "," + "Mean Value" +"\n") //column headers
k=range(8,15)
for i in k:
    q=range(i)
    g=str(mean(q))   
    myFile.write(str(i) + "," + g +"\n")
myFile.close() 

should give you 2 columns when opened in excel. One with the ID one with the mean value

Comments

[MartyMcFly]

that will print only the mean value of the last list in the txt file. I'd like to have a list with all the mean values.