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Recent advances in piezoresistive materials have opened the possibility of developing pressure sensitive flexible mats that cover large areas. They are composed of arrays of sensitive cells. However, in many configurations proposed in the literature, the measurement of a single cell does not recover the cell resistance itself but the equivalent resistance between the row and column conductive strips that select it. If this effect is not corrected, unloaded regions can appear with non negligible pressure, as a kind of ghost object. Diodes can be placed to overcome the problem, but this makes the fabrication more complex, especially for prototypes. In this paper, we propose a novel software solution based on a circuit analysis of the mat. The set of cell resistances is obtained from the set of equivalent resistances between row and columns. Several algorithms are compared. For simulated values of the array, the true cell resistance can be recovered with a great accuracy. A good compromise between execution speed and error is achieved by a Newton-Krylov nonlinear solver. Nevertheless, this algorithm presents convergence problems when facing values of a real mat. In this case a fixed-point formulation is more appropriate. For $16 \times 16$ arrays, it can achieve relative errors with a mean value of 0.0258 in less than 0.1 s running on a regular PC. The removal of ghost objects is also shown visually. [ABSTRACT FROM AUTHOR]