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Posted to commits@echarts.apache.org by GitBox <gi...@apache.org> on 2021/12/29 08:22:55 UTC

[GitHub] [echarts] pissang opened a new pull request #16300: [Feature] [axis] add alignTicks for mutliple axis alignment.

pissang opened a new pull request #16300:
URL: https://github.com/apache/echarts/pull/16300

## Brief Information

This pull request is in the type of:

- [ ] bug fixing
- [x] new feature
- [ ] others

### What does this PR do?

This PR adds `alignTicks` option to allow ticks alignment between multiple value or log axis.

Similar PR: https://github.com/apache/echarts/pull/13210

### How it Works

When a value/log axis is set to `alignTicks: true`. It will find the first value/log axis on the same dimension that is not use `alignTicks` and align the ticks to it. The align algorithm is bacially from radar series, which already has ticks alignment between multiple indicator axis, with some enhancement on the corner cases. Here is a simple explanation:

1. Get the ticks number of axis align to. The `splitNumber` is `ticksNumber - 1`
2. Calculate `extent` and `interval` with this `splitNumber` using `calcNiceExtent`.
3. The calculated ticks is not excatly same to the target number. So we need an extra refine step, the refine step will consider four cases:
+ If `min` and `max` are both fixed. It will simply calculate the `interval` by `(max - min) / splitNumber`
+ If `max` is fixed. Try to calculate `min` by `max - interval * splitNumber`. `interval` is from the second step. If the calculated `min` is larger than the minimal value. Increase interval util `min` is less than the minimal value.
+ If `min` is fixed. Similar to `max` fixed case.
+ If both `min` and `max` are not fixed. Set `max` to `extent[1]` calculated from the second step. Then it's similar to the `max` fixed case. Note if the calculated `min` and `max` cross the zero value. We need to check if the data extent cross and make sure they are both positive or negative.
4. If the axis align to has set `min` or `max`. We need to adjust the calculated `min` and `max` proportionally.

### Limitations

1. Time axis is not supported yet because the ticks calculation has becoming really complex since 5.0
2. Using `alignTicks` with complex `min`, `max` value, e.g. `'dataMin'`, `'dataMax'`, will lead to unreadable ticks.

### Fixed issues

https://github.com/apache/echarts/issues/11390
https://github.com/apache/echarts/issues/10928

## Details

### Before: What was the problem?

![image](https://user-images.githubusercontent.com/841551/147641667-3a7f272f-ed5d-4be6-a631-b39d5bb7b883.png)

### After: How is it fixed in this PR?

![image](https://user-images.githubusercontent.com/841551/147641612-0f6bf3dd-59e5-4bb4-a2cb-96ba1aab6f36.png)

### More conformance tests

![image](https://user-images.githubusercontent.com/841551/147641796-0606535f-6b25-4aec-92e5-fb580705ff4d.png)

## Misc

- [x] The API has been changed (apache/echarts-doc#xxx).
- [ ] This PR depends on ZRender changes (ecomfe/zrender#xxx).

### Related test cases or examples to use the new APIs

N.A.

## Others

### Merging options

- [ ] Please squash the commits into a single one when merging.

### Other information

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