Why is my np.arccos not working in my for loop?-CodePudding

I have a for loop with a formula whit gives the following error:

 RuntimeWarning: invalid value encountered in arccos
  test3[i] = np.arccos(temp.x[i])

If I perform the formula withouth the np.arccos, it works. Does anyone know why the np.arccos is preventing the formula to work?

This is my simplified for loop:

for i in range(1,len(temp)):
    test3[i] = np.arccos(temp.x[i])

EDIT

This is my df named temp:

                         time      x      y      z  bat
0     2022-05-16 12:22:58.719  0.276  0.101 -0.919  NaN
1     2022-05-16 12:23:23.719  0.264  0.085 -0.927  NaN
2     2022-05-16 12:23:48.719  0.276  0.105 -0.906  NaN
3     2022-05-16 12:24:13.719  0.260  0.101 -0.919  NaN
4     2022-05-16 12:24:38.719  0.272  0.105 -0.915  NaN
                      ...    ...    ...    ...  ...
96376 2022-06-13 09:39:38.719 -0.083 -0.014 -0.957  NaN
96377 2022-06-13 09:40:03.719 -0.087 -0.018 -0.949  NaN
96378 2022-06-13 09:40:28.719 -0.094 -0.018 -0.962  NaN
96379 2022-06-13 09:40:53.719 -0.083 -0.018 -0.944  NaN
96380 2022-06-13 09:41:18.719 -0.551  0.006 -0.940  NaN

EDIT 2

And to make test3 variable i used:

test3 = np.zeros(len(temp))

EDIT 3 Other numpy function do seem to work, like this one:

test3[i] = np.sqrt(temp.x[i-1]**2   temp.y[i-1]**2   temp.z[i-1]**2)

EDIT 4

Now I remove my above 1 and below -1 values I get a new error:

Traceback (most recent call last):

File "C:\ProgramData\Anaconda3\lib\site-packages\pandas\core\indexes\base.py", line 3361, in get_loc return self._engine.get_loc(casted_key)

File "pandas_libs\index.pyx", line 76, in pandas._libs.index.IndexEngine.get_loc

File "pandas_libs\index.pyx", line 108, in pandas._libs.index.IndexEngine.get_loc

File "pandas_libs\hashtable_class_helper.pxi", line 2131, in pandas._libs.hashtable.Int64HashTable.get_item

File "pandas_libs\hashtable_class_helper.pxi", line 2140, in pandas._libs.hashtable.Int64HashTable.get_item

KeyError: 632

The above exception was the direct cause of the following exception:

Traceback (most recent call last):

  File "C:\Users\untitled5.py", line 61, in <module>
    test3[i] = np.arccos(temp.x[i])# * temp.x[i-1]   temp.y[i] * temp.y[i-1]   temp.z[i] * temp.z[i-1])/(np.sqrt(temp.x[i]**2   temp.y[i]**2   temp.z[i]**2)) * np.sqrt(temp.x[i-1]**2   temp.y[i-1]**2   temp.z[i-1]**2)

  File "C:\ProgramData\Anaconda3\lib\site-packages\pandas\core\series.py", line 942, in __getitem__
    return self._get_value(key)

  File "C:\ProgramData\Anaconda3\lib\site-packages\pandas\core\series.py", line 1051, in _get_value
    loc = self.index.get_loc(label)

  File "C:\ProgramData\Anaconda3\lib\site-packages\pandas\core\indexes\base.py", line 3363, in get_loc
    raise KeyError(key) from err

KeyError: 632

CodePudding user response：

I solved the problem thanks to everyone,

I removed the above 1 and -1 values, which is just a small part of my dataset:

temp = temp.loc[(temp["x"] <= 1)
                & (temp["x"] >= -1)
                [(temp["y"] <= 1)
                 & (temp["y"] >= -1)]
                [(temp["z"] <= 1)
                 & (temp["z"] >= -1)]]

EDIT

And because of removing some of the rows, the index becomes not 1, 2, 3, 4, 5, but 1,5,10 etc. This will break the for loop. To restore this use reindex with drop - True:

temp = temp.reset_index(drop=True)

CodePudding user response：

arccos only takes values between -1 and 1 inclusive. If you check temp.max(axis=1) and temp.min(axis=1) it will tell you whether one of the values of any of the columns is outside of that range.

CodePudding user response：

Limited to the interval [-1,1]?