Question

我想改变潘达斯数据框架中的具体价值。这里是一个实例数据框架(在现实中,还有许多方面):

              Value                       Property
0               CH4                       Type
1          -10.90979                      Density (g/cm3)
2           5.00000                       Temperature (K)

在这里,我想将“10.90979”乘以“代码>10在“<1>上加标签。我不想写“10.90979 * 10”,因为我只知道我拥有一个称为“(g/cm3)的财产。我不知道它的价值。因此,我想使用“Density (g/cm3)的行文索引出现在倍增中。

我已尝试:

row_index = df.index.get_loc(df[df[ Property ] ==  Density (g/cm3) ].index[0])
new_value = df.iloc[row_index][0] * 10
df["Value"].replace(df.iloc[row_index][0], new_value, inplace=True)

然而,这给我带来了令人ir慕的产出。我收到了:

              Value                       Property
0               CH4                       Type
1 -10.90979-10.90979...                   Density (g/cm3)
2           5.00000                       Temperature (K)

我可以说出该法典的细节,但希望有人会承认一个简单的错误。我确信,在数据框架中,使用多复制的电离层是正确的。我也试图利用这一手段。

df.iloc[row_index][0].mul(10)

但有错误<代码>。 AttributeError: str Object has no Depende mul .

谁能向我指出正确的方向?

Answer 1

你的问题是,由于<代码> CH4 <代码>Value栏的数值,该栏的数值在你试图乘数时作为指示处理;

 -10.90979 *10 =  -10.90979-10.90979-10.90979...

你们需要将价值转换为浮动值,以进行操作。请注意:booleanindexing , 查阅所有Density:

mask = df[ Property ] ==  Density (g/cm3) 
df.loc[mask,  Value ] = df.loc[mask,  Value ].astype(float) * 10

产出:

      Value         Property
0       CH4             Type
1 -109.0979  Density (g/cm3)
2   5.00000  Temperature (K)

Answer 2

<><><>>>>

http://www.un.org/Depts/DGACM/index_spanish.htm

cond = df[ Property ].eq( Density (g/cm3) )
df.assign(Value=df[ Value ].where(cond).astype( float ).mul(10).fillna(df[ Value ]))

注:

      Value         Property
0       CH4             Type
1 -109.0979  Density (g/cm3)
2   5.00000  Temperature (K)

www.un.org/Depts/DGACM/index_spanish.htm 例

import pandas as pd
data1 = { Value : [ CH4 ,  -10.90979 ,  5.00000 ], 
          Property : [ Type ,  Density (g/cm3) ,  Temperature (K) ]}
df = pd.DataFrame(data1)

Answer 3

正如其他人指出的,你的<代码>Value栏不是数字(由于<代码>CH4第一数值)。但更根本的是,你为什么想要将密度乘以<条码>10<>/代码>? 问题越高?

From this question (and your previous one, now deleted), it looks like you have chemical compounds and are trying to do unit conversions on their physical properties. I would recommend looking into packages that do that readily. For example: pint and its pandas companion pint_pandas.

看来,您的化学化合物(例如,或 CH4 )的数据Frams作为第一行的价值,然后是一些物理特性。


You may be better off using dicts to represent your properties. E.g.:
from pint import UnitRegistry

Q_ = UnitRegistry().Quantity

compounds = {
     CH4 : dict(
        name= methane ,
        molar_mass=Q_(16.043,  g / mol ),
        density_0=Q_(0.657,  kg/m**3 ),
        at_0=Q_(25,  °C ),
        density_1=Q_(0.717,  kg/m**3 ),
        at_1=Q_(0,  °C ),
        density_2=Q_(422.8,  g/L ),
        at_2=Q_(-162,  °C ),
    ),
     SO2 : dict(
        name= sulfur dioxide ,
        molar_mass=Q_(64.066,  g / mol ),
        density_0=Q_(2.6288,  kg / m**3 ),
        at_0=Q_(25,  °C ),
    ),
}

然后,如果你愿意的话,你可以将此转化为数据框架:
import pandas as pd
import pint_pandas

df = pd.DataFrame(compounds).T

将一栏具体改为某些理想的单位,例如:
>>> df[ density_0 ].astype( pint[g/L] )
CH4    0.6570000000000001
SO2    2.6288000000000005

a. 整个数据基
z = df.astype(dict(
    molar_mass= pint[g/mol] ,
    density_0= pint[g/L] ,
    density_1= pint[g/L] ,
    density_2= pint[g/L] ,
    at_0= pint[degC] ,
    at_1= pint[degC] ,
    at_2= pint[degC] ,
))

>>> z
               name  molar_mass           density_0  at_0           density_1  at_1  density_2  at_2
CH4         methane      16.043  0.6570000000000001    25  0.7170000000000001     0      422.8  -162
SO2  sulfur dioxide      64.066  2.6288000000000005    25                 nan   nan        nan   nan

>>> z.dtypes
name                        object
molar_mass       pint[gram / mole]
density_0       pint[gram / liter]
at_0          pint[degree_Celsius]
density_1       pint[gram / liter]
at_1          pint[degree_Celsius]
density_2       pint[gram / liter]
at_2          pint[degree_Celsius]
dtype: object

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