Classification of simulated data. This figure shows a set of images, (a) is a projection from a noise-free map of the herpes virus. (b) is a noisy version of (a), a simulated noise was added to the projection, the level of noise is equivalent to that of JEOL 4000 microscope. (c) shows the Fourier-filtered version of (b). A classification of the filtered data has been made. In order to assess this classification, it is necessary to compare the noise free projection with the class average, which includes a filtered version of this projection. After classification of Fourier-filtered data, the average particle of the class, including the particle in (c), is calculated and shown in (f). (d) is the wavelet-filtered version of (b). After classification of wavelet filtered particles, the average of the class, including the particle in (d), is shown in (e).