Note

This page is a reference documentation. It only explains the class signature, and not how to use it. Please refer to the user guide for the big picture.

8.4.1. nilearn.decomposition.CanICA

class nilearn.decomposition.CanICA(mask=None, n_components=20, smoothing_fwhm=6, do_cca=True, threshold='auto', n_init=10, random_state=None, standardize=True, standardize_confounds=True, detrend=True, low_pass=None, high_pass=None, t_r=None, target_affine=None, target_shape=None, mask_strategy='epi', mask_args=None, memory=Memory(location=None), memory_level=0, n_jobs=1, verbose=0)

Perform Canonical Independent Component Analysis [1] [2].

Parameters
maskNiimg-like object or MultiNiftiMasker instance, optional

Mask to be used on data. If an instance of masker is passed, then its mask will be used. If no mask is given, it will be computed automatically by a MultiNiftiMasker with default parameters.

n_componentsint, optional

Number of components to extract. Default=20.

smoothing_fwhmfloat, optional

If smoothing_fwhm is not None, it gives the size in millimeters of the spatial smoothing to apply to the signal. Default=6mm.

do_ccaboolean, optional

Indicate if a Canonical Correlation Analysis must be run after the PCA. Default=True.

standardizeboolean, optional

If standardize is True, the time-series are centered and normed: their mean is put to 0 and their variance to 1 in the time dimension. Default=True.

standardize_confoundsboolean, optional

If standardize_confounds is True, the confounds are zscored: their mean is put to 0 and their variance to 1 in the time dimension. Default=True.

detrendboolean, optional

If detrend is True, the time-series will be detrended before components extraction. Default=True.

thresholdNone, ‘auto’ or float, optional

If None, no thresholding is applied. If ‘auto’, then we apply a thresholding that will keep the n_voxels, more intense voxels across all the maps, n_voxels being the number of voxels in a brain volume. A float value indicates the ratio of voxels to keep (2. means that the maps will together have 2 x n_voxels non-zero voxels ). The float value must be bounded by [0. and n_components]. Default=’auto’.

n_initint, optional

The number of times the fastICA algorithm is restarted Default=10.

random_stateint or RandomState, optional

Pseudo number generator state used for random sampling.

target_affine3x3 or 4x4 matrix, optional

This parameter is passed to image.resample_img. Please see the related documentation for details.

target_shape3-tuple of integers, optional

This parameter is passed to image.resample_img. Please see the related documentation for details.

low_passNone or float, optional

This parameter is passed to signal.clean. Please see the related documentation for details

high_passNone or float, optional

This parameter is passed to signal.clean. Please see the related documentation for details

t_rfloat, optional

This parameter is passed to signal.clean. Please see the related documentation for details

mask_strategy{‘epi’, ‘background’, or ‘template’}, optional

The strategy used to compute the mask: use ‘background’ if your images present a clear homogeneous background, ‘epi’ if they are raw EPI images, or you could use ‘template’ which will extract the gray matter part of your data by resampling the MNI152 brain mask for your data’s field of view. Depending on this value, the mask will be computed from masking.compute_background_mask, masking.compute_epi_mask or masking.compute_brain_mask. Default=’epi’.

mask_argsdict, optional

If mask is None, these are additional parameters passed to masking.compute_background_mask or masking.compute_epi_mask to fine-tune mask computation. Please see the related documentation for details.

memoryinstance of joblib.Memory or string, optional

Used to cache the masking process. By default, no caching is done. If a string is given, it is the path to the caching directory. Default=Memory(location=None).

memory_levelinteger, optional

Rough estimator of the amount of memory used by caching. Higher value means more memory for caching. Default=0.

n_jobsinteger, optional

The number of CPUs to use to do the computation. -1 means ‘all CPUs’, -2 ‘all CPUs but one’, and so on. Default=1.

verboseinteger, optional

Indicate the level of verbosity. By default, nothing is printed Default=0.

References

1

G. Varoquaux et al. “A group model for stable multi-subject ICA on fMRI datasets”, NeuroImage Vol 51 (2010), p. 288-299

2

G. Varoquaux et al. “ICA-based sparse features recovery from fMRI datasets”, IEEE ISBI 2010, p. 1177

Attributes
`components_`2D numpy array (n_components x n-voxels)

Masked ICA components extracted from the input images. They can be unmasked thanks to the masker_ attribute.

Deprecated since version 0.4.1. Use components_img_ instead.

`components_img_`4D Nifti image

4D image giving the extracted ICA components. Each 3D image is a component.

New in version 0.4.1.

`masker_`instance of MultiNiftiMasker

Masker used to filter and mask data as first step. If an instance of MultiNiftiMasker is given in mask parameter, this is a copy of it. Otherwise, a masker is created using the value of mask and other NiftiMasker related parameters as initialization.

`mask_img_`Niimg-like object

See http://nilearn.github.io/manipulating_images/input_output.html The mask of the data. If no mask was given at masker creation, contains the automatically computed mask.

__init__(mask=None, n_components=20, smoothing_fwhm=6, do_cca=True, threshold='auto', n_init=10, random_state=None, standardize=True, standardize_confounds=True, detrend=True, low_pass=None, high_pass=None, t_r=None, target_affine=None, target_shape=None, mask_strategy='epi', mask_args=None, memory=Memory(location=None), memory_level=0, n_jobs=1, verbose=0)

Initialize self. See help(type(self)) for accurate signature.

fit(imgs, y=None, confounds=None)

Compute the mask and the components across subjects

Parameters
imgslist of Niimg-like objects

See http://nilearn.github.io/manipulating_images/input_output.html Data on which the mask is calculated. If this is a list, the affine is considered the same for all.

confoundslist of CSV file paths or numpy.ndarrays or pandas DataFrames, optional

This parameter is passed to nilearn.signal.clean. Please see the related documentation for details. Should match with the list of imgs given.

Returns
selfobject

Returns the instance itself. Contains attributes listed at the object level.

fit_transform(X, y=None, **fit_params)

Fit to data, then transform it.

Fits transformer to X and y with optional parameters fit_params and returns a transformed version of X.

Parameters
Xarray-like of shape (n_samples, n_features)

Input samples.

yarray-like of shape (n_samples,) or (n_samples, n_outputs), default=None

Target values (None for unsupervised transformations).

**fit_paramsdict

Additional fit parameters.

Returns
X_newndarray array of shape (n_samples, n_features_new)

Transformed array.

get_params(deep=True)

Get parameters for this estimator.

Parameters
deepbool, default=True

If True, will return the parameters for this estimator and contained subobjects that are estimators.

Returns
paramsdict

Parameter names mapped to their values.

inverse_transform(loadings)

Use provided loadings to compute corresponding linear component combination in whole-brain voxel space

Parameters
loadingslist of numpy array (n_samples x n_components)

Component signals to tranform back into voxel signals

Returns
reconstructed_imgslist of nibabel.Nifti1Image

For each loading, reconstructed Nifti1Image

score(imgs, confounds=None, per_component=False)

Score function based on explained variance on imgs.

Should only be used by DecompositionEstimator derived classes

Parameters
imgsiterable of Niimg-like objects

See http://nilearn.github.io/manipulating_images/input_output.html Data to be scored

confoundsCSV file path or numpy.ndarray or pandas DataFrame, optional

This parameter is passed to nilearn.signal.clean. Please see the related documentation for details

per_componentbool, optional

Specify whether the explained variance ratio is desired for each map or for the global set of components. Default=False.

Returns
scorefloat

Holds the score for each subjects. Score is two dimensional if per_component is True. First dimension is squeezed if the number of subjects is one

set_params(**params)

Set the parameters of this estimator.

The method works on simple estimators as well as on nested objects (such as Pipeline). The latter have parameters of the form <component>__<parameter> so that it’s possible to update each component of a nested object.

Parameters
**paramsdict

Estimator parameters.

Returns
selfestimator instance

Estimator instance.

transform(imgs, confounds=None)

Project the data into a reduced representation

Parameters
imgsiterable of Niimg-like objects

See http://nilearn.github.io/manipulating_images/input_output.html Data to be projected

confoundsCSV file path or numpy.ndarray or pandas DataFrame, optional

This parameter is passed to nilearn.signal.clean. Please see the related documentation for details

Returns
loadingslist of 2D ndarray,

For each subject, each sample, loadings for each decomposition components shape: number of subjects * (number of scans, number of regions)