使用自定义阈值舍入数字

Question

如果它超过了一个阈值(不是0.5),那么我希望能够"舍入"一个数字,否则向下舍入.

这是我提出的一些糟糕的代码.在matlab中是否有内置函数,或更优雅的解决方案(矢量化可能)？

function [ rounded_numbers ] = custom_round( input_numbers, threshold )
%CUSTOM_ROUND rounds between 0 and 1 with threshold threshold

  [input_rows, input_cols] = size(input_numbers);
  rounded_numbers = zeros(input_rows, input_cols);

  for i = 1:length(input_numbers)
    if input_numbers(i) > threshold
      rounded_numbers(i) = 1;
    else
      rounded_numbers(i) = 0;
    end
  end
end

谢谢

Answer 1

只是用

round(x - treshold + 0.5)

测试用例:

>> x = -10:0.3:10
ans =
    -2   -1.7  -1.4  -1.1  -0.8  -0.5  -0.2  0.1    0.4   0.7    1    1.3   1.6   1.9


>> treshold = 0.8; % round everything up for which holds mod(x,1) >= treshold
>> y = round(x-treshold+0.5)

ans =
    -2    -2    -2    -1    -1    -1    -1     0     0     0     1     1     1     2

正数也正确舍入,除了在边界上:-0.8舍入到-1而不是0,但这与圆正常的行为相同:round(-0.5)返回-1

Answer 2

这是一个解决方案，如果数字超过阈值，我们会从零舍入

in = [0.2,-3.3,4.1];
th = 0.2;

%# get the fractional part of the number
frac = mod(in,1); %# positive for negative in

%# find the sign so we know whether to round
%# to plus or minus inf
sig = sign(in);

%# identify which way to round
upIdx = frac>th; %# at threshold, we round down

%# round towards inf if up
out = abs(in);
out(upIdx) = ceil(out(upIdx));
out(~upIdx) = floor(out(~upIdx));
%# re-set the sign
out= out.*sig
out =
 0    -4     4

注意：如果数字只在 0 到 1 之间，那就更简单了：

%# this does exactly what your code does
out = double(in>th);