Backport PR #25586 on branch 0.24.x (BUG: secondary y axis could not be set to log scale (#25545))
Backport PR #25586: BUG: secondary y axis could not be set to log scale (#25545)
# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25599?src=pr&el=h1) Report
> Merging [#25599](https://codecov.io/gh/pandas-dev/pandas/pull/25599?src=pr&el=desc) into [0.24.x](https://codecov.io/gh/pandas-dev/pandas/commit/1577b0ee4e59c0f767a7b2923dbc5ccfe56434a3?src=pr&el=desc) will **decrease** coverage by `<.01%`.
> The diff coverage is `50%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/25599/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/25599?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           0.24.x   #25599      +/-   ##
==========================================
- Coverage   92.39%   92.39%   -0.01%     
==========================================
  Files         166      166              
  Lines       52419    52421       +2     
==========================================
  Hits        48433    48433              
- Misses       3986     3988       +2
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.83% <50%> (-0.01%)` | :arrow_down: |
| #single | `42.9% <0%> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/25599?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/plotting/\_core.py](https://codecov.io/gh/pandas-dev/pandas/pull/25599/diff?src=pr&el=tree#diff-cGFuZGFzL3Bsb3R0aW5nL19jb3JlLnB5) | `83.53% <50%> (-0.05%)` | :arrow_down: |
| [pandas/util/testing.py](https://codecov.io/gh/pandas-dev/pandas/pull/25599/diff?src=pr&el=tree#diff-cGFuZGFzL3V0aWwvdGVzdGluZy5weQ==) | `88.04% <0%> (-0.1%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25599?src=pr&el=continue).
> **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta)
> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25599?src=pr&el=footer). Last update [1577b0e...b6c77ad](https://codecov.io/gh/pandas-dev/pandas/pull/25599?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25599?src=pr&el=h1) Report
> Merging [#25599](https://codecov.io/gh/pandas-dev/pandas/pull/25599?src=pr&el=desc) into [0.24.x](https://codecov.io/gh/pandas-dev/pandas/commit/1577b0ee4e59c0f767a7b2923dbc5ccfe56434a3?src=pr&el=desc) will **decrease** coverage by `<.01%`.
> The diff coverage is `50%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/25599/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/25599?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           0.24.x   #25599      +/-   ##
==========================================
- Coverage   92.39%   92.39%   -0.01%     
==========================================
  Files         166      166              
  Lines       52419    52421       +2     
==========================================
  Hits        48433    48433              
- Misses       3986     3988       +2
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.83% <50%> (-0.01%)` | :arrow_down: |
| #single | `42.9% <0%> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/25599?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/plotting/\_core.py](https://codecov.io/gh/pandas-dev/pandas/pull/25599/diff?src=pr&el=tree#diff-cGFuZGFzL3Bsb3R0aW5nL19jb3JlLnB5) | `83.53% <50%> (-0.05%)` | :arrow_down: |
| [pandas/util/testing.py](https://codecov.io/gh/pandas-dev/pandas/pull/25599/diff?src=pr&el=tree#diff-cGFuZGFzL3V0aWwvdGVzdGluZy5weQ==) | `88.04% <0%> (-0.1%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25599?src=pr&el=continue).
> **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta)
> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25599?src=pr&el=footer). Last update [1577b0e...b6c77ad](https://codecov.io/gh/pandas-dev/pandas/pull/25599?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
