Replace value in array with condition

Question

I have this simplified program to replace values in array which fulfill the conditions:

formula1=2*2
formula2=5*2
formula3=4*4

array = np.random.rand(2,4,10)
for n,i in enumerate(array):
    if i>0.5: #find value in array with this condition
        formula = formula1
        array[n] = array[n]*formula #replace the found value with this value
    elif i <0.1:
        formula = formula2
        array[n] = array[n]*formula
    else:
        formula = formula3
        array[n] = array[n]*formula
print array

It resulted in error message:'The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()'. Any suggestion?

@syntonym if i<0.5: ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all() — F L
– F L, Commented Jun 21, 2016 at 10:37
In your for loop, i is an array. How would you determine if an array is lesser than a given value? any() checks if any of the elements in the array is lesser than the given value and all() checks if all the elements are — SvbZ3r0
– SvbZ3r0, Commented Jun 21, 2016 at 10:38
@SvbZ3r0 isn't any() or all() used to find boolean value of True and False only? — F L
– F L, Commented Jun 21, 2016 at 10:41
Not necessarily. Try np.any(array<0.5) to see if any of the values in array are lesser than 0.5 — SvbZ3r0
– SvbZ3r0, Commented Jun 21, 2016 at 10:44

Jacques Gaudin · Accepted Answer · 2016-06-21 11:14:19Z

3

To enumerate an array, you can use np.ndenumerate (documentation here):

for n, i in np.ndenumerate(array):
    ...

edited Jun 21, 2016 at 11:14

answered Jun 21, 2016 at 10:41

Jacques Gaudin

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