Recently, Tony Williams enquired whether there had been any comparisons of the CDK with other tools for the calculation of polar surface area (PSA) and logP. Given that PSA calculations using the fragments defined by Ertl et al are pretty straightforward, it’s not surprising that the CDK implementation matches very well with the ACD Labs […]
Caching SMARTS Queries
Andrew Dalke recently published a detailed write up on his implementation of the Pubchem fingerprints and provided a pretty thorough comparison with the CDK implementation. He pointed out a number of bugs in the CDK version; but he also noted that performance could be improved by caching parsed SMARTS queries – which are used extensively […]
Visualizing PAINS SMARTS
A few days ago I had made available a SMARTS version of the PAINS substructural filters, that were converted using CACTVS from the original SLN patterns. I had mentioned that the SMARTSViewer application was a handy way to visualize the complex SMARTS patterns. Matthias Rarey let me know that his student had converted all the […]
Similarity Matrices in Parallel
Today I got an email asking whether it’d be possible to speed up a fingerprint similarity matrix calculation in R. Now, pairwise similarity matrix calculations (whether they’re for molecules or sequences or anything else) are by definition quadratic in nature. So performing these calculations for large collections aren’t always feasible – in many cases, it’s […]
Inserting 2D Depictions into R Plots
Recent versions of rcdk allow you to insert images of chemical structures into R plots, via the view.image.2d and rasterImage functions. One problem with the latter function is that the 2D structure image must be located in plot units, rather than pixel units. Paul Murrell suggested an easy way to insert the raster image into […]