scanpy.external.pp.mnn_correct(*datas, var_index=None, var_subset=None, batch_key='batch', index_unique='-', batch_categories=None, k=20, sigma=1.0, cos_norm_in=True, cos_norm_out=True, svd_dim=None, var_adj=True, compute_angle=False, mnn_order=None, svd_mode='rsvd', do_concatenate=True, save_raw=False, n_jobs=None, **kwargs)

Correct batch effects by matching mutual nearest neighbors [Haghverdi18] [Kang18].

This uses the implementation of mnnpy [Kang18].

Depending on do_concatenate, returns matrices or AnnData objects in the original order containing corrected expression values or a concatenated matrix or AnnData object.

Be reminded that it is not advised to use the corrected data matrices for differential expression testing.

More information and bug reports here.

datas : AnnData | ndarrayUnion[AnnData, ndarray]

Expression matrices or AnnData objects. Matrices should be shaped like n_obs × n_vars (n_cell × n_gene) and have consistent number of columns. AnnData objects should have same number of variables.

var_index : Collection[str] | NoneOptional[Collection[str]] (default: None)

The index (list of str) of vars (genes). Necessary when using only a subset of vars to perform MNN correction, and should be supplied with var_subset. When datas are AnnData objects, var_index is ignored.

var_subset : Collection[str] | NoneOptional[Collection[str]] (default: None)

The subset of vars (list of str) to be used when performing MNN correction. Typically, a list of highly variable genes (HVGs). When set to None, uses all vars.

batch_key : strstr (default: 'batch')

The batch_key for concatenate(). Only valid when do_concatenate and supplying AnnData objects.

index_unique : strstr (default: '-')

The index_unique for concatenate(). Only valid when do_concatenate and supplying AnnData objects.

batch_categories : Collection[Any] | NoneOptional[Collection[Any]] (default: None)

The batch_categories for concatenate(). Only valid when do_concatenate and supplying AnnData objects.

k : intint (default: 20)

Number of mutual nearest neighbors.

sigma : floatfloat (default: 1.0)

The bandwidth of the Gaussian smoothing kernel used to compute the correction vectors. Default is 1.

cos_norm_in : boolbool (default: True)

Whether cosine normalization should be performed on the input data prior to calculating distances between cells.

cos_norm_out : boolbool (default: True)

Whether cosine normalization should be performed prior to computing corrected expression values.

svd_dim : int | NoneOptional[int] (default: None)

The number of dimensions to use for summarizing biological substructure within each batch. If None, biological components will not be removed from the correction vectors.

var_adj : boolbool (default: True)

Whether to adjust variance of the correction vectors. Note this step takes most computing time.

compute_angle : boolbool (default: False)

Whether to compute the angle between each cell’s correction vector and the biological subspace of the reference batch.

mnn_order : Sequence[int] | NoneOptional[Sequence[int]] (default: None)

The order in which batches are to be corrected. When set to None, datas are corrected sequentially.

svd_mode : {‘svd’, ‘rsvd’, ‘irlb’}Literal[‘svd’, ‘rsvd’, ‘irlb’] (default: 'rsvd')

'svd' computes SVD using a non-randomized SVD-via-ID algorithm, while 'rsvd' uses a randomized version. 'irlb' perfores truncated SVD by implicitly restarted Lanczos bidiagonalization (forked from

do_concatenate : boolbool (default: True)

Whether to concatenate the corrected matrices or AnnData objects. Default is True.

save_raw : boolbool (default: False)

Whether to save the original expression data in the raw attribute.

n_jobs : int | NoneOptional[int] (default: None)

The number of jobs. When set to None, automatically uses scanpy._settings.ScanpyConfig.n_jobs.


optional keyword arguments for irlb.

Return type

Tuple[Union[ndarray, AnnData], List[DataFrame], Optional[List[Tuple[Optional[float], int]]]]Tuple[Union[ndarray, AnnData], List[DataFrame], Optional[List[Tuple[Optional[float], int]]]]


datasndarray | AnnDataUnion[ndarray, AnnData]

Corrected matrix/matrices or AnnData object/objects, depending on the input type and do_concatenate.


A list containing MNN pairing information as DataFrames in each iteration step.

angle_listList[Tuple[Optional[float], int]] | NoneOptional[List[Tuple[Optional[float], int]]]

A list containing angles of each batch.