1.繪制腦電頭皮圖
在上一篇文章中導入腦電數據的基礎上，我們在eeglab plot的界面選擇：Edit->Channel locations選擇配置通道位置文件。如果導入的數據為Neuroscan或BioSemi格式，則通道位置不需要配置，已經包含在數據集中。
調用通道編輯窗口時，如圖下所示：

選擇第二個模板，表示執行本地源，使用MNI坐標點擊OK出現一下界面：

在這里我們導入事先準備好的通道文件，同時，點擊Read locs help按鈕可以查看這里支持的通道文件格式：

the file extension determines its type.'.loc' or '.locs' or '.eloc': polar coordinates. Notes: angles in degrees: right ear is 90; left ear -90; head disk radius is 0.5. Fields: N angle radius labelSample: 1 -18 .511 Fp1 2 18 .511 Fp2 3 -90 .256 C34 90 .256 C4...Note: In previous releases, channel labels had to contain exactly four characters (spaces replaced by '.'). This format still works, though dots are no longer required.'.sph':Matlab spherical coordinates. Notes: theta is the azimuthal/horizontal anglein deg.: 0 is toward nose, 90 rotated to left ear. Following this, performsthe elevation (phi). Angles in degrees.Fields: N theta phi labelSample: 1 18 -2 Fp12 -18 -2 Fp23 90 44 C34 -90 44 C4...'.elc':Cartesian 3-D electrode coordinates scanned using the EETrak software. See readeetraklocs().'.elp': Polhemus-.'elp' Cartesian coordinates. By default, an .elp extension is readas PolhemusX-elp in which 'X' on the Polhemus sensor is pointed toward the subject. Polhemus files are not in columnar format (see readelp()).'.elp':BESA-'.elp' spherical coordinates: Need to specify 'filetype','besa'.The elevation angle (phi) is measured from the vertical axis. Positive rotation is toward right ear. Next, perform azimuthal/horizontal rotation (theta): 0 is toward right ear; 90 is toward nose, -90 toward occiput. Angles are in degrees. If labels are absent or weights are given in a last column, readlocs() adjusts for this. Default labels are E1, E2, ...Fields: Type label phi theta Sample: EEG Fp1 -92 -72 EEG Fp2 92 72 EEG C3 -46 0 EEG C4 46 0 ...'.xyz': Matlab/EEGLAB Cartesian coordinates. Here. x is towards the nose, y is towards the left ear, and z towards the vertex. Note that the firstcolumn (x) is -Y in a Matlab 3-D plot, the second column (y) is X in a matlab 3-D plot, and the third column (z) is Z.Fields: channum x y z labelSample: 1 .950 .308 -.035 Fp12 .950 -.308 -.035 Fp23 0 .719 .695 C34 0 -.719 .695 C4...'.asc', '.dat': Neuroscan-.'asc' or '.dat' Cartesian polar coordinates text file.'.mat': Brainstrom channel location file.'.sfp': BESA/EGI-xyz Cartesian coordinates. Notes: For EGI, x is toward right ear, y is toward the nose, z is toward the vertex. EEGLAB converts EGI Cartesian coordinates to Matlab/EEGLAB xyz coordinates. Fields: label x y zSample: Fp1 -.308 .950 -.035 Fp2 .308 .950 -.035 C3 -.719 0 .695 C4 .719 0 .695 ...'.ced': ASCII file saved by pop_chanedit(). Contains multiple MATLAB/EEGLAB formats.Cartesian coordinates are as in the 'xyz' format (above).Fields: channum label theta radius x y z sph_theta sph_phi ...Sample: 1 Fp1 -18 .511 .950 .308 -.035 18 -2 ...2 Fp2 18 .511 .950 -.308 -.035 -18 -2 ...3 C3 -90 .256 0 .719 .695 90 44 ...4 C4 90 .256 0 -.719 .695 -90 44 ......The last columns of the file may contain any other defined fields (gain,calib, type, custom).

點擊“Read locations”按鈕，選擇sample_data文件中“eeglab_chan32.locs”，加載通道文件。在下一個彈窗中如果不指定文件格式，將自動按文件擴展名來評估其格式：

點擊OK，在下面界面中通道坐標和極坐標都顯示出來，其中繪制在頭部外部的電極是位于頭部中線以下的電極，點擊OK再選擇Plot->Channel location->By name將頭皮電極圖可視化，顯示電極名稱，或者選擇Plot->Channel location->By number顯示通道名稱。

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2.繪制通道對應光譜圖

在eeglab界面選擇Plot->Channel spectra and maps得到下面界面：

在Percent data to sample輸入框內更改采樣率為15，即展示當采樣為15%數據時得到的結果，也可以默認設置為100，得到結果分別如下圖：

??????????上圖中每一個彩色記錄通道表示一個數據通道活動的頻譜。最上邊的頭皮圖顯示了分別在6、10、22Hz時頭皮的能量分布，數據分別集中在腦部不同位置。同時也可以選擇繪制不同通道數據的頭皮位置及活動范圍及其活動在單個時期的ERP圖像。選擇Plot->Channel properties，在index中選擇需要查看的通道：

這里填寫通道10，點擊OK出現如下界面：
其中紅點為所選通道在頭皮上的位置，右上角的圖表示其活動范圍及其活動在單個時期的ERP圖像

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