The DiffLogo tool is a R package for the visualization of differences between multiple motifs for different alphabets. The user supplies a set of motifs each represented as position weight matrices (PWMs) [1]. The DiffLogo package supports the comparison of two motifs by a single DiffLogo and the comparison of multiple motifs by a DiffLogo-table. DiffLogo is based on the idea behind the well-known sequence logo [2], i.e. motifs are visualized position-wise based on two functions. First, the stackHeight function computes the height of each stack. Second, the baseDistribution function breaks down the stack height on the individual characters. The user is able to parametrise the individual functions with arbitrary functions stackHeight and baseDistribution. Default implementations of both functions are provided.

DiffLogo is designed for researchers with any biological background and interest in computational biology. It is useful to document findings, share knowledge, and to present the outcome of motif prediction pipelines. It aims at an increase of the quality of comparative publications. In addition, DiffLogo eases the communication between bioinformatics scientists and biologists.

DiffLogo is intended for the comparison of similar motifs. These motifs can come from different sources such as

• different treatments, species, cell lines, or tissues
• different motif prediction algorithms and configurations

Download and install the R package DiffLogo available in the folder 'built'. Load your motifs of interest as PWMs [1] to R. Please find example motifs in the file 'exampleLogos.R' and in the folder 'inst/pwm' (extracted from [3]). Please find the vignette 'DiffLogoBasics.Rnw' of the DiffLogo package for example code.

Use the function diffLogoFromPwm(PWM1, PWM2) to visualize the difference between two motifs.

Use the function diffLogoTable(listOfPWMs) to visualize the pairwise difference between more than two motifs.

[1] http://en.wikipedia.org/wiki/Position_weight_matrix
[2] Schneider TD, Stephens RM. 1990. Sequence Logos: A New Way to Display Consensus Sequences. Nucleic Acids Res. 18:6097-6100
[3] Eggeling, R., Gohr, A., Keilwagen, J., Mohr, M., Posch, S., Smith, A.D., Grosse, I.: On the value of intra-motifdependencies of human insulator protein ctcf. PLoS ONE 9(1), 85629 (2014). doi:10.1371/journal.pone.0085629