glm.singlestudy_tmap
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| — | glm.singlestudy_tmap [2010/08/24 13:39] (current) – created jochen | ||
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| + | ====== GLM:: | ||
| + | ===== Motivation ===== | ||
| + | After running the regression for a single study (run, i.e. one FMR, VTC, or MTC object), creating t-contrast maps for just this study can be beneficial in determining whether or not a certain run contains too much noise (or specific artefacts) for it to be included in second-level statistics. Also, it is sometimes desired to use the actually standard-error-normalized effect-statistic (t instead of regression beta) for further computations (e.g. to incorporate a measure of within-subject-data noise on the second level). | ||
| + | |||
| + | ===== Requirements ===== | ||
| + | You need to have a GLM file/object available that represents the regression outcome of a single run. **Please note that, at this time, the support for FMR (MAP creation) has not been implemented; | ||
| + | |||
| + | ===== Method reference (' | ||
| + | < | ||
| + | |||
| + | FORMAT: | ||
| + | |||
| + | Input fields: | ||
| + | |||
| + | c NxC contrast vector (default: full model and main eff) | ||
| + | mapopts | ||
| + | | ||
| + | | ||
| + | |||
| + | Output fields: | ||
| + | |||
| + | map | ||
| + | |||
| + | ===== Reference notes ===== | ||
| + | **The '' | ||
| + | |||
| + | ===== Usage example ===== | ||
| + | Say you have a study with 5 regressors of interest and 1 confound (mean study level, automatically added by BrainVoyager QX/ | ||
| + | |||
| + | * instruction | ||
| + | * motion in left visual field | ||
| + | * motion in right visual field | ||
| + | * motion in both visual fields (at the same time) | ||
| + | * static (trials without any motion) | ||
| + | |||
| + | then the syntax to create a contrast over all conditions sharing motion in any visual field would be coded as: | ||
| + | |||
| + | <code matlab glm_singlestudy_tmap_ex1.m> | ||
| + | glm = xff(' | ||
| + | |||
| + | % create the contrast | ||
| + | contrast = glm.SingleStudy_tMap([0; | ||
| + | |||
| + | % name the contrast | ||
| + | contrast.Map.Name = ' | ||
| + | |||
| + | % save the contrast | ||
| + | contrast.SaveAs; | ||
| + | |||
| + | % clean up | ||
| + | contrast.ClearObject; | ||
| + | glm.ClearObject;</ | ||
| + | |||
| + | ===== Usage notes ===== | ||
| + | Please note the following details about this method and the example: | ||
| + | |||
| + | * at this time, the name of the contrast(s) cannot be specified but has to be set after the call | ||
| + | * multiple contrasts can be given whereas the number of contrasts is the number of columns in the weights argument | ||
| + | * each contrast should either have its weights be all positive (or all negative, weighted contrast over baseline, or reversed) or sum up to 0 (weighted differential contrast between conditions); | ||
glm.singlestudy_tmap.txt · Last modified: 2010/08/24 13:39 by jochen
