> For the complete documentation index, see [llms.txt](https://zh-1-peng.gitbook.io/fmri-notes/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://zh-1-peng.gitbook.io/fmri-notes/smooth-fwhm.md).

# smooth FWHM

covert FWHM in voxel to in mm

```
load SPM.mat;

M = SPM.xVol.M;

VOX = sqrt(diag(M(1:3,1:3)'*M(1:3,1:3)))';

FWHM = SPM.xVol.FWHM;

FWHMmm= FWHM.\*VOX;

disp\(FWHMmm\)
```

when you specified a 5mm FWHM, the real one will be around 8 after caculation when you specified a 4mm FWHM, the real onw will be around 7.5 after caculation