Understanding of the nature of dark energy , which appears to drive the expansion of the universe , is one of the central problems of physical cosmology today .
In an earlier paper [ Daly & Djorgovski ( 2003 ) ] we proposed a novel method to determine the expansion rate E ( z ) and the deceleration parameter q ( z ) in a largely model-independent way , directly from the data on coordinate distances y ( z ) .
Here we expand this methodology to include measurements of the pressure of dark energy p ( z ) , its normalized energy density fraction f ( z ) , and the equation of state parameter w ( z ) .
We then apply this methodology to a new , combined data set of distances to supernovae and radio galaxies .
In evaluating E ( z ) and q ( z ) , we make only the assumptions that the FRW metric applies , and that the universe is spatially flat ( an assumption strongly supported by modern CMBR measurements ) .
The determinations of E ( z ) and q ( z ) 
are independent of any theory of gravity .
For evaluations of p ( z ) , f ( z ) and w ( z ) , a theory of gravity must be adopted , and General Relativity is assumed here .
No a priori assumptions regarding the properties or redshift evolution of the dark energy are needed .
We obtain trends for y ( z ) and E ( z ) which are fully consistent with the standard Friedmann-Lemaitre concordance cosmology with \Omega _ { 0 } = 0.3 and \Lambda _ { 0 } = 0.7 .
The measured trend for q ( z ) deviates systematically from the predictions of this model on a \sim 1 - 2 ~ { } \sigma level , but may be consistent for smaller values of \Lambda _ { 0 } .
We confirm our previous result that the universe transitions from acceleration to deceleration at a redshift z _ { T } \approx 0.4 .
The trends for p ( z ) , f ( z ) , and w ( z ) are consistent with being constant at least out to z \sim 0.3 - 0.5 , and broadly consistent with being constant out to higher redshits , but with large uncertainties .
For the present values of these parameters we obtain : E _ { 0 } = 0.97 \pm 0.03 , q _ { 0 } = -0.35 \pm 0.15 , p _ { 0 } = -0.6 \pm 0.15 , f _ { 0 } = -0.62 - ( \Omega _ { 0 } -0.3 ) \pm 0.05 , and w _ { 0 } = -0.9 - \epsilon ( \Omega _ { 0 } -0.3 ) \pm 0.1 , where \Omega _ { 0 } is the density parameter for nonrelativistic matter , and \epsilon \approx 1.5 \pm 0.1 .
We note that in the standard Friedmann-Lemaitre models p _ { 0 } = - \Lambda _ { 0 } , and thus we can measure the value of the cosmological constant directly , and obtain results in agreement with other contemporary results .