[Introduction]  [Signal arithmetic]  [Signals and noise]   [Smoothing]   [Differentiation]  [Peak Sharpening]  [Harmonic analysis]   [Fourier convolution]  [Fourier deconvolution]  [Fourier filter]   [Peak area measurement]  [Linear Least Squares]  [Multicomponent Spectroscopy]  [Iterative Curve Fitting]  [Hyperlinear quantitative absorption spectrophotometry] [Appendix and Case Studies]  [Peak Finding and Measurement]  [iPeak]   [iSignal]  [Peak Fitters]   [iFilter]  [iPower]  [List of downloadable software]  [Interactive tools]

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Who uses this Web site and its associated documents and software?

In the last few years, this web site (http://terpconnect.umd.edu/~toh/spectrum/) has been accessed from Internet Service Providers in over 162 countries and 6 non-region-specific categories (e.g. satellite providers), including many developing countries, some very small countries (e.g. Liechtenstein, the Faroe Islands), relatively isolated countries (Cuba, North Korea, Myanmar/Burma), and even some war-torn regions (Afghanistan, Syria, Iraq). Internet access is often an issue. For example, I've got fewer hits from Cuba that from other Spanish-speaking countries with smaller populations, such as Bolivia, Dominican Republic, Costa Rica, Puerto Rico, Panama, and Uruguay, even though Cuba has many active scientists, especially in the medical and pharmaceutical fields.

The first Web version went up in 1996, but I didn't start keeping track of hits until 2008; since then there have been over 1.8 million page views. The distribution of page view (hit) counts among countries is very long-tailed, with one-third of the hits coming from the USA (except during major US holidays), half of the hits coming from only 5 countries (USA, India, Germany, United Kingdom, and China) and 99% of the hits coming from only 39 countries. Among the countries that have a relatively large number of page views relative to their populations are the USA, Germany, UK, Canada, Australia, Netherlands, Switzerland, Singapore, Israel, Belgium, Taiwan, South Korea, and Scandinavia. 

The Internet Service Providers with the largest number of hits are Comcast, Verizon FIOS, Time Warner, Cloudflare, At&t U-verse, Deutsche Telekom (Germany), BSNL (India), and Cox Communication. Most hits worldwide come from Windows machines, about 20% from Linux and Macintosh, and 10% from mobile devices. I've made efforts to make my pages more usable from mobile devices like smartphones.

About one quarter of the hits come directly from educational institution ISPs that have "School", "Ecole", "College", "Hochschule", "Univ...", "Academic", or "Institute of Technology" in their names. (The number of educational users is certainly larger than that because some users are no doubt accessing from other ISPs in homes or businesses). An analysis of 200,000 hits over the last year shows that the biggest educational users have been the
University of California System (UCLA, Berkley, etc.), Indian Institute Of Technology system, the University of Texas system, Massachusetts Institute Of Technology, The University of Michigan, the University of Maryland, Delft University of Technology (Netherlands), Stanford University, China Education And Research Network Center,  the University Of Wisconsin System, and The University of Illinois.

Many of the large national laboratories are users, including Bell Canada,
Oak Ridge, Pacific Northwest, Lawrence Livermore, Sandia, Brookhaven, National Renewable Energy Laboratory, SLAC, FermiLab, Lawrence Berkeley, NRC Canada, CERN, NIST, NASA, JPL, and NIH.

The most popular pages on the site recently have been
Peak Finding and Measurement, Smoothing, Integration, InteractivePeakFitter, and Signal Processing Tools. About 50% of the page views originate from search engines (80% of those using Google). The most common search keywords used are: "peak area", "convolution", "deconvolution", "peak detection", "signal processing pdf", "findpeaks matlab", "Fourier filter", and "smoothing". About 40% of the traffic comes from direct links (bookmarks or typed URLs) and about 10% comes from referring websites, usually from Wikipedia or from MathWorks. Unfortunately, page loads and search terms are becoming increasingly encrypted in recent years, so which pages are being viewed and what is being download are becoming harder to know.

There have been over 100,000 downloads of my software and documentation files, currently averaging about 500-1000 file downloads per month. The most commonly downloaded files are IntroToSignalProcessing.pdf, PeakFinder.zip, ipf11.zip, CurveFitter....xlsx, iSignal5.zip, ipeak7.zip, PeakDetection.xlsxand the complete site archive SPECTRUM.zip.
 
What factors influence the number of hits from different countries?  The tools of data analysis can help answer this question. Obviously one would expect that a country's population would be a factor, but it turns out that the correlation between page loads and population is very poor, with a coefficient of determination (correlation coefficient or R2 value) of only 0.36 (n=163 countries; over 160,000 total page loads).

I also investigated the effect of other factors, including the number of English speakers, the number of Internet users, the number of universities, and the total research and development budget of each country. By a good margin, the most influential factor was the
research and development budget, for which the R2 value was 0.76. This is perhaps not surprising given that my site concerns a very narrow and specialized topic: the technical aspects of computerized scientific data processing.

A multilinear regression on all 5 of these factors yielded a R2 value of 0.84 (n=53 countries for which all 5 factors were reported), which is a modest improvement over the research and development budget alone.

For an Excel spreadsheet with all these data and calculations (as of May, 2015), see FinalCountriesSummary.xlsx


What fields of study are represented?  The users of my site include students, instructors, workers, and researchers in industry, environmental, medical, engineering, earth science, space, military, financial, agriculture, communications, and even music and linguistics. This conclusion is based on emails I have received, on the titles of journal articles that have cited my work, and on the ISPs of major web visitors. A list of specific application areas on which readers are working is given in applications.pdf. As of May 2016, my site and its programs had been cited in over 160 published papers and patents.

Pageloads vs population, (May 2015)


This page is part of "A Pragmatic Introduction to Signal Processing", created and maintained by Prof. Tom O'Haver , Department of Chemistry and Biochemistry, The University of Maryland at College Park. Comments, suggestions and questions should be directed to Prof. O'Haver at toh@umd.edu.  Updated August, 2016
Unique visits to this site since June 17, 2008: