measurement

My question has to do with the physical meaning of the results of doing a spectral analysis of a signal, or of throwing the signal into an FFT and interpreting what comes out using a suitable numerical package, Specifically: take a signal, say a time-varying voltage v(t) throw it into an FFT (you get back a sequence of complex numbers) now take the modulus (abs) and square the result, i.e. |fft(v)|^2. So you now have real numbers on the y axis -- shall I call these spectral coefficients? using the sampling resolution, you follow a cookbook recipe and associate the spectral coefficients to

Is there a web developer functionality/tool that allows us to know how many times a browser is doing reflows? basically I want to have some sort of feedback/information. I don't know how it will be, but perhaps some sort of performance graph that shows the timeline (akin to Google's Speed Tracer ) so I can investigate when suddenly at a point the browser is doing an insane amount of reflows so I can point out hey here's a bottleneck, there got to be a bug/bad implementation of something here or something. Chrome and Safari have Timeline tab in Web Inspector where you can see all the reflows

I'd like to print a string based on a Measurement but limit it to 2 digits. I am using the MeasurementFormatter for this. var beans:Measurement = Measurement(value: 20.22321, unit: UnitMass.milligrams) // "20.22321 mg" let formatter = MeasurementFormatter() formatter.numberFormatter.maximumFractionDigits = 2 let label = formatter.string(from: beans) // 0 lb I expected 20.22 mg as a results, not 0 lb . Where's my mistake? You need to set the MeasurementFormatter property unitOption to .providedUnit let beans = Measurement(value: 20.22321, unit: UnitMass.milligrams) // "20.22321 mg" let

My app is supposed to estimate the length (in millimeters) of an object using euro coins as reference. This is a screenshot example: To get the diameter of the photographed coin I first calculate the equation of a the circle passing through those 3 points of the form x^2 + y^2 + ax + by + c = 0 and then I have the diameter by 2 * square_root((a/2)^2 + (b/2)^2 -c) . Finally I can perform the following proportion to get the length of the red pen: /* length_estimated_pen (mm) : distance_green_pins (points) = real_diameter_coin (mm) : diameter_on_screen (points) */ let distanceGreen:Double =

For a particular segment of Java code, I'd like to measure: Execution time (most likely thread execution time ) Memory usage CPU load (specifically attributable to the code segment) I'm a relative Java novice and am not familiar with how this might be achieved. I've been referred to JMX , however I'm not sure how that might be used, and JMX looks a bit 'heavy' for what I'm looking to do. Ideally I'd like some measurement class that can be told what I would like to measure, with the option of calling a start() method prior to a code segment and a stop() method after. Relevant metrics would be

The documentation says that 160 dp (density-independent) equals 1 inch. And 72 pt is also 1 inch. So I don't see why android define a dp measurement while it seems to work the same as points. Can anybody explain that? Why should I use dp if I can use pt? John Leehey The Android documentation used to incorrectly state that 160 dp always equals 1 inch regardless of screen density. This was reported as a bug which was accepted and the documentation updated. From the updated documentation: 160 dp will NOT always equal 1 inch, it will vary with different screen sizes and densities. On a screen with

I'm writing a small program in C, and I want to measure it's performance. I want to see how much time do it run in the processor and how many cache hit+misses has it made. Information about context switches and memory usage would be nice to have too. The program takes less than a second to execute. I like the information of /proc/[pid]/stat, but I don't know how to see it after the program has died/been killed. Any ideas? EDIT: I think Valgrind adds a lot of overhead. That's why I wanted a simple tool, like /proc/[pid]/stat, that is always there. Use perf : perf stat ./yourapp See the kernel

I just want to know if the pixel unit is something that doesn't change, and if we can convert from pixels to let's say centimeters ? Mark Ransom Similar to this question which asks about points instead of centimeters. There are 72 points per inch and there are 2.54 centimeters per inch, so just substitute 2.54 for 72 in the answer to that question. I'll quote and correct my answer here: There are 2.54 centimeters per inch; if it is sufficient to assume 96 pixels per inch, the formula is rather simple: centimeters = pixels * 2.54 / 96 There is a way to get the configured pixels per inch of your