Added create_power_operator in sugar.py

nifty/sugar.py

+# -*- coding: utf-8 -*-
+
+from nifty import PowerSpace,\
+                  Field,\
+                  DiagonalOperator,\
+                  FFTOperator
+
+__all__ = ['create_power_operator']
+
+
+def create_power_operator(domain, power_spectrum, distribution_strategy='not'):
+    if not domain.harmonic:
+        fft = FFTOperator(domain)
+        domain = fft.target[0]
+
+    power_domain = PowerSpace(domain)
+
+    fp = Field(power_domain,
+               val=power_spectrum,
+               distribution_strategy=distribution_strategy)
+
+    f = fp.power_synthesize(mean=1, std=0)
+
+    power_operator = DiagonalOperator(domain, diagonal=f)
+
+    return power_operator