How can i set the contrast in SLM?

[Ashley95555]

• What is the current behavior?
  Now, I expected the results of the interaction effect of gender and group on cortical thickness, but I have no idea how how to set the contrast.

• Please provide the steps to reproduce and if possible a minimal demo of the problem.

contrast_sex_int = (demographics.group .* ...
                    (demographics.gender == "F")) - ...
                   (demographics.group .* ...
                   (demographics.gender == "M"));

• What is the expected behavior?
  Wish your reply

• Please tell us about your computing environment:
  Matlab R2022a

• Other information

[zihuaihuai]

Please refer to this section of the tutorial

Next, we must define a contrast in observations (here: age). With the model, contrast, and cortical thickness data, we can then assess whether there is an effect of age on cortical thickness.
contrast_age = demographics.AGE_AT_SCAN;
mask = fetch_mask('fsaverage5');

slm = SLM( ...
model, ...
contrast_age, ...
'surf', 'fsaverage5', ...
'correction', {'rft', 'fdr'}, ...
'cluster_threshold', 0.01, ...
'mask', mask);
slm.fit(cortical_thickness);

Before we go any further, we can quickly assess the quality and robustness of the fitted model. We can do this for every vertex/parcel on the cortex (default), for one vertex (see example below for vertex #88), or for a set of specific vertices. Our function slm.qc outputs a histogram of the residuals and a qq plot of the residuals versus the theoretical quantile values from a normal distribution. We can also map vertexwise measures of skewness and kurtosis (characterizing the residuals distribution) across the cortex.

If anything is not clear or wrong in the tutorial, feel free to submit a new issue about tutorial, please.