o=frgramian(c, F); o=frgramian(c, Fa, Fs);
| c | Input coefficients |
| Fa | Analysis frame |
| Fs | Synthesis frame |
| o | Output coefficients |
o=frgramian(c,F) applies the Gramian operator or Gram matrix of the frame F. The entries of the Gram matrix are the inner products of the frame elements of F. The frame must have been created using frame. If the frame F is a Parseval frame, the Gramian operator is a projection onto the range of the frame analysis operator.
o=frgramian(c, Fa, Fs) applies the (cross) Gramian operator with the frames Fa and Fs. Here Fs is the frame associated with the frame synthesis operator and Fa the frame that is associated with the frame analysis operator. The entries of the matrix that is constructed through the Gramian operator are the inner products of the frame elements of Fa and Fs. If Fa and Fs are canonical dual frames, the Gramian operator is a projection onto the range of the frame analysis operator.