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Hi, I want to perform a power analysis and I read that I need 3 of 4 things: 1. Effect size (mean/std) 2. False positive rate 3. Number of subjects 4. True positive rate
I also read that the effect size can be calculated using gamma.mgh and gammavar.mgh files but I do not know how to open them in order to get the numbers.
Thank you, Laura
The gamma and gammavar files are vertex-wise values. You can load them in matlab with something like g = MRIread('gamma.mgh'); gv = MRIread('gammavar.mgz'); but you will need the vertex that you are interested in (or do for all vertices). You can use fast_glm_power.m in the FSFAST toolbox to compute the power (requires stats toolbox).
On 12/11/18 6:39 AM, Laura Ferrero wrote:
External Email - Use CautionHi, I want to perform a power analysis and I read that I need 3 of 4 things:
- Effect size (mean/std)
- False positive rate
- Number of subjects
- True positive rate
I also read that the effect size can be calculated using gamma.mgh and gammavar.mgh files but I do not know how to open them in order to get the numbers.
Thank you, Laura
Freesurfer mailing list Freesurfer@nmr.mgh.harvard.edu https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer
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Dear Douglas,
I performed the statistical analysis using stats files so I do not have vertex information, I assume it will be cortical regions information. Is the approach to read them the same? Thank you, Laura
El 11 dic 2018, a las 16:54, Greve, Douglas N.,Ph.D. DGREVE@mgh.harvard.edu escribió:
The gamma and gammavar files are vertex-wise values. You can load them in matlab with something like g = MRIread('gamma.mgh'); gv = MRIread('gammavar.mgz'); but you will need the vertex that you are interested in (or do for all vertices). You can use fast_glm_power.m in the FSFAST toolbox to compute the power (requires stats toolbox).
On 12/11/18 6:39 AM, Laura Ferrero wrote:
External Email - Use CautionHi, I want to perform a power analysis and I read that I need 3 of 4 things:
- Effect size (mean/std)
- False positive rate
- Number of subjects
- True positive rate
I also read that the effect size can be calculated using gamma.mgh and gammavar.mgh files but I do not know how to open them in order to get the numbers.
Thank you, Laura
Freesurfer mailing list Freesurfer@nmr.mgh.harvard.edu https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer
Freesurfer mailing list Freesurfer@nmr.mgh.harvard.edu https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer
yes, same approach
On 12/11/2018 12:21 PM, Laura Ferrero wrote:
External Email - Use CautionDear Douglas,
I performed the statistical analysis using stats files so I do not have vertex information, I assume it will be cortical regions information. Is the approach to read them the same? Thank you, Laura
El 11 dic 2018, a las 16:54, Greve, Douglas N.,Ph.D. DGREVE@mgh.harvard.edu escribió:
The gamma and gammavar files are vertex-wise values. You can load them in matlab with something like g = MRIread('gamma.mgh'); gv = MRIread('gammavar.mgz'); but you will need the vertex that you are interested in (or do for all vertices). You can use fast_glm_power.m in the FSFAST toolbox to compute the power (requires stats toolbox).
On 12/11/18 6:39 AM, Laura Ferrero wrote:
External Email - Use CautionHi, I want to perform a power analysis and I read that I need 3 of 4 things:
- Effect size (mean/std)
- False positive rate
- Number of subjects
- True positive rate
I also read that the effect size can be calculated using gamma.mgh and gammavar.mgh files but I do not know how to open them in order to get the numbers.
Thank you, Laura
Freesurfer mailing list Freesurfer@nmr.mgh.harvard.edu https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer
Freesurfer mailing list Freesurfer@nmr.mgh.harvard.edu https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer
Freesurfer mailing list Freesurfer@nmr.mgh.harvard.edu https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer
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After using MRIread from Matlab in file gamma.mgh, I obtain the following: mri =
struct with fields:
srcbext: '' analyzehdr: [] bhdr: [] vol: [] fspec: 'gamma.mgh' pwd: '/Users/lauraferrero/Documents/MATLAB' flip_angle: 0 tr: 0 te: 0 ti: 0 vox2ras0: [4×4 double] volsize: [1 34 1] height: 1 width: 34 depth: 1 nframes: 1 vox2ras: [4×4 double] nvoxels: 34 xsize: 1 ysize: 1 zsize: 1 x_r: 1 x_a: 0 x_s: 0 y_r: 0 y_a: 1 y_s: 0 z_r: 0 z_a: 0 z_s: 1 c_r: 0 c_a: 0 c_s: 0 vox2ras1: [4×4 double] Mdc: [3×3 double] volres: [1 1 1] tkrvox2ras: [4×4 double]
But I do not know which field corresponds to the mean for the effect size. Regards, Laura
El 11 dic 2018, a las 18:21, Laura Ferrero lauraferrero12@gmail.com escribió:
Dear Douglas,
I performed the statistical analysis using stats files so I do not have vertex information, I assume it will be cortical regions information. Is the approach to read them the same? Thank you, Laura
El 11 dic 2018, a las 16:54, Greve, Douglas N.,Ph.D. DGREVE@mgh.harvard.edu escribió:
The gamma and gammavar files are vertex-wise values. You can load them in matlab with something like g = MRIread('gamma.mgh'); gv = MRIread('gammavar.mgz'); but you will need the vertex that you are interested in (or do for all vertices). You can use fast_glm_power.m in the FSFAST toolbox to compute the power (requires stats toolbox).
On 12/11/18 6:39 AM, Laura Ferrero wrote:
External Email - Use CautionHi, I want to perform a power analysis and I read that I need 3 of 4 things:
- Effect size (mean/std)
- False positive rate
- Number of subjects
- True positive rate
I also read that the effect size can be calculated using gamma.mgh and gammavar.mgh files but I do not know how to open them in order to get the numbers.
Thank you, Laura
Freesurfer mailing list Freesurfer@nmr.mgh.harvard.edu https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer
Freesurfer mailing list Freesurfer@nmr.mgh.harvard.edu https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer
freesurfer@nmr.mgh.harvard.edu
-
Greve, Douglas N.,Ph.D. -
Laura Ferrero