Metrics and covariates are structures to organize non-timeseries and non-MRI measures. Examples include surveys, BP measures, and polysomnography scoring.

Covariates

A "covariate" is a stored value. The covariate has a name, and will be either a number or text ("string"). It will usually have a date (and possibly time) when it was measured.

The covariate information is stored in the "covariate" table. The actual values are stored separately as values in the "covariate_value" table.

Covariate table

Read only
'covariate_id'	'int(11)'	'NO'	'PRI'	''	'auto_increment'
'modified'	'timestamp'	'NO'	''	'CURRENT_TIMESTAMP'	'on update CURRENT_TIMESTAMP'
Required
'name'	'varchar(255)'	'NO'	''	''	''
'valtype'	'enum(''number'',''string'')'	'YES'	''	''	''
Optional
'valdefault'	'varchar(255)'	'YES'	''	''	''
'category'	'varchar(255)'	'YES'	''	''	''
'description'	'varchar(4096)'	'YES'	''	''	''
'parent_covariate_id'	'int(11)'	'YES'	''	''	''
'formula'	'varchar(2048)'	'YES'	''	''	''

Covariate_value table

Read only
'covariate_value_id'	'int(11)'	'NO'	'PRI'	''	'auto_increment'
'modified'	'timestamp'	'NO'	''	'CURRENT_TIMESTAMP'	'on update CURRENT_TIMESTAMP'
Required
'subject_id'	'int(11)'	'NO'	''	''	''
'covariate_id'	'int(11)'	'NO'	''	''	''
'value'	'varchar(255)'	'YES'	''	''	''
Optional
'name'	'varchar(255)'	'YES'	''	''	''
'datetime'	'datetime'	'YES'	''	''	''
'projectgroupstudy_id'	'int(11)'	'YES'	''	''	''
'analysissetgroupstudy_id'	'int(11)'	'YES'	''	''	''
'tag'	'varchar(1024)'	'YES'	''	''	''
'comment'	'varchar(2048)'	'YES'	''	''	''

Metrics

A metric is a way to group several covariates. For example, if you do a survey with several questionnaires, each questionnaire can be saved as a covariate value, but if you have a lot of questionnaires, it will become unwieldy. A metric could be "MRI visit survey" and consist of the questions and questionnaires asked on the day of the MRI visit. You can then link this to a study in a project. For example, to link polysomnography scores to a study with MRI's and physiology, create a new study "metric" and then in the project link that to the study, just like you link an MRI series or physiology recording.

A "metric" is just a type of study associated with the subject, set in the subjects GUI. A separate very simple table records all covariate_values in that metric.

Protocol ID for metric

You can use the same format of protocol id for the metric as for MRI and physiology; because studies are selected by type, an MRI and metric with the same protocol id will not get confused.

[patient id][session number][yyyymmdd]

Table metric

'study_id'	'int(11)'	'NO'
'covariate_value_id'	'int(11)'	'NO'

Note that one metric could have repeated entries - this might be useful to make up for missing data (I'm not sure). And of course one metric can be used in multiple project studies.

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