feat(sampler): add min-max sampler function

[snukhulov]

Brief Information

This pull request is in the type of:

• bug fixing
• new feature
• others

What does this PR do?

Add min-max sampler function

Details

Before: What was the problem?

In some cases min-max sampling algorithm fits line data more naturally than the existing ones. For example, for a sine with a lot of data points min-max sampler is the best choice.

Example.
The original sine without sampling (200 000 data points).

Using 'average' sampler

Using 'lttb' sampler

Using 'max' sampler

Using 'min' sampler

After: How does it behave after the fixing?

Using new 'minmax' sampler

Document Info

One of the following should be checked.

• This PR doesn't relate to document changes
• The document should be updated later
• The document changes have been made in feat(sampler): add min-max sampler function echarts-doc#374

Misc

ZRender Changes

• 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

[echarts-bot]

Thanks for your contribution!
The community will review it ASAP. In the meanwhile, please checkout the coding standard and Wiki about How to make a pull request.

Document changes are required in this PR. Please also make a PR to apache/echarts-doc for document changes and update the issue id in the PR description. When the doc PR is merged, the maintainers will remove the PR: awaiting doc label.

[github-actions]

The changes brought by this PR can be previewed at: https://echarts.apache.org/examples/editor?version=PR-19279@4a63340

[Ovilia]

This seems to be a great idea. Can you explain what min-max mean first?

[snukhulov]

This seems to be a great idea. Can you explain what min-max mean first?

Thank you.
Like 'min' sampler that highlights an extremum (turning-point) at a local minimum and like 'max' sampler that highlights an extremum at a local maximum, 'minmax' sampler highlights the larger extremum (minimum or maximum extremum in absolute comparison) at a frame of data points.
'minmax' sampler is suitable for sine or other periodic data

[Ovilia]

Thanks for your explanation. Can you provide a link or something for further understanding? Is this a concept well-known or you invented it?

[snukhulov]

Thanks for your explanation. Can you provide a link or something for further understanding? Is this a concept well-known or you invented it?

It's my own implementation of the known min-max downsampling algorithm

[Ovilia]

Thanks! Please also add test cases in test/line-sampling.html. Please pay special attention both to the cases where there are negative values or not.

[snukhulov]

Thanks! Please also add test cases in test/line-sampling.html. Please pay special attention both to the cases where there are negative values or not.

I added the described test cases

[Ovilia]

Thanks for your contribution! This will be released in the next version.

[Ovilia]

Updated demo here

[echarts-bot]

Congratulations! Your PR has been merged. Thanks for your contribution! 👍