[Numpy-discussion] Rounding float to integer while minizing the difference between the two arrays?

[Chao YUE]

Sorry, there is one error in this part of code, it should be:


def convert_integer(x,threshold=0):
    """
    This fucntion converts the float number x to integer according to the
threshold.
    """
    if abs(x-0) < 1e-5:
        return 0
    else:
        pdec,pint = math.modf(x)
        if pdec > threshold:
            return int(math.ceil(pint)+1)
        else:
            return int(math.ceil(pint))



On Wed, Jul 16, 2014 at 3:18 PM, Chao YUE <chaoyuejoy at gmail.com> wrote:

> Dear all,
>
> I have two arrays with both float type, let's say X and Y. I want to round
> the X to integers (intX) according to some decimal threshold, at the same
> time I want to limit the following difference as small:
>
> diff = np.sum(X*Y) - np.sum(intX*Y)
>
> I don't have to necessarily minimize the "diff" variable (If with this
> demand the computation time is too long). But I would like to limit the
> "diff" to, let's say ten percent within np.sum(X*Y).
>
> I have tried to write some functions, but I don't know where to start the
> opitimization.
>
> def convert_integer(x,threshold=0):
>     """
>     This fucntion converts the float number x to integer according to the
> threshold.
>     """
>     if abs(x-0) < 1e5:
>         return 0
>     else:
>         pdec,pint = math.modf(x)
>         if pdec > threshold:
>             return int(math.ceil(pint)+1)
>         else:
>             return int(math.ceil(pint))
>
> def convert_arr(arr,threshold=0):
>     out = arr.copy()
>     for i,num in enumerate(arr):
>         out[i] = convert_integer(num,threshold=threshold)
>     return out
>
> In [147]:
> convert_arr(np.array([0.14,1.14,0.12]),0.13)
>
> Out[147]:
> array([1, 2, 0])
>
> Now my problem is, how can I minimize or limit the following?
> diff = np.sum(X*Y) - np.sum(convert_arr(X,threshold=?)*Y)
>
> Because it's the first time I encounter such kind of question, so please
> give me some clue to start :p Thanks a lot in advance.
>
> Best,
>
> Chao
>
> --
> please visit:
> http://www.globalcarbonatlas.org/
>
> ***********************************************************************************
> Chao YUE
> Laboratoire des Sciences du Climat et de l'Environnement (LSCE-IPSL)
> UMR 1572 CEA-CNRS-UVSQ
> Batiment 712 - Pe 119
> 91191 GIF Sur YVETTE Cedex
> Tel: (33) 01 69 08 29 02; Fax:01.69.08.77.16
>
> ************************************************************************************
>



-- 
please visit:
http://www.globalcarbonatlas.org/
***********************************************************************************
Chao YUE
Laboratoire des Sciences du Climat et de l'Environnement (LSCE-IPSL)
UMR 1572 CEA-CNRS-UVSQ
Batiment 712 - Pe 119
91191 GIF Sur YVETTE Cedex
Tel: (33) 01 69 08 29 02; Fax:01.69.08.77.16
************************************************************************************
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