python - 如何将标量值添加到 yt 数组？

Question

我正在尝试向我在 yt 中的派生字段之一添加一个数字下限。但是，当我尝试时: new_field = 1.0e-10 + data['metal_density']

我收到以下错误:

In [1]: ad = ds.all_data()

In [2]: floored_density = 1.0e-10 + ad['density'] yt : [INFO     ] 2014-09-26 10:15:21,901 Gathering a field list (this may take a moment.) yt : [INFO     ] 2014-09-26 10:15:22,275 Loading field plugins. yt : [INFO     ] 2014-09-26 10:15:22,275 Loaded angular_momentum (8 new fields) yt : [INFO     ] 2014-09-26 10:15:22,276 Loaded astro (14 new fields) yt : [INFO     ] 2014-09-26 10:15:22,276 Loaded cosmology (20 new fields) yt : [INFO     ] 2014-09-26 10:15:22,276 Loaded fluid (56 new fields) yt : [INFO     ] 2014-09-26 10:15:22,277 Loaded fluid_vector (88 new fields) yt : [INFO ] 2014-09-26 10:15:22,278 Loaded geometric (102 new fields) yt : [INFO ] 2014-09-26 10:15:22,278 Loaded local (102 new fields) yt : [INFO     ] 2014-09-26 10:15:22,278 Loaded magnetic_field (108 new fields) yt : [INFO     ] 2014-09-26 10:15:22,278 Loaded species (108 new fields)
--------------------------------------------------------------------------- YTUnitOperationError                      Traceback (most recent call last) /home/skillman/yt-x86_64/src/yt-3.0/yt/mods.pyc in <module>()
----> 1 floored_density = 1.0e-10 + ad['density']

/home/skillman/yt-x86_64/src/yt-3.0/yt/units/yt_array.pyc in
__radd__(self, left_object)
    674     def __radd__(self, left_object):
    675         """ See __add__. """
--> 676         lo = sanitize_units_add(self, left_object, "addition")
    677         return YTArray(super(YTArray, self).__radd__(lo))
    678 

/home/skillman/yt-x86_64/src/yt-3.0/yt/units/yt_array.pyc in sanitize_units_add(this_object, other_object, op_string)
    159     else:
    160         if not inp.units.is_dimensionless:
--> 161             raise YTUnitOperationError(op_string, inp.units, dimensionless)
    162     return ret
    163 

YTUnitOperationError: The addition operator for YTArrays with units (g/cm**3) and (1) is not well defined.

Answer 1

只要注意要添加的标量与 yt 数组的单位相同，就可以执行以下操作:

ad = ds.all_data()

floored_density = 1.0e-10 * ad['density'].uq + ad['density']

.uq 代表“单位数量”，在相关字段的单位中等于 1.0。在这种情况下，ad['密度'].uq 等于 1.0 g/cm**3。

此处描述了与 yt 数组 Hook 的其他有用属性:http://yt-project.org/doc/analyzing/units/symbolic_units.html?highlight=unit_quantity#Creating-arrays-and-quantities