math

问题 I am trying to find a user through their Bluetooth strength (RSSI value). I have 3 Raspberry PIs, each gathering the signal strength of the user. Lets say the nodes returned: node1 = 65 node2 = 70 node3 = 75 How would I find the user through triangulation and pin point them on a map, and output the RSSI value? I have researched Trilateration and Ceva's Theorem but do not know how to implement them. I am unsure on how to locate the nodes in an environment, do I give the main node a location of

问题 In C and C++, the modf function can break floating number into fractional and integral parts. I'm curious about what does "modf" stand for. What is it shorthand for? 回答1: what is modf() shorthand for? The function breaks a floating point number up into whole number and fractional parts. Looking at the 1989 definition (I do not find it in K & R 1st Ed.)... The modf function break the argument value into integral and fractional parts, each of which has the same sign as the argument. It stores

问题 I am trying to make a shader in Unity taking a mercator projection texture as a source and converting it to an equirectangular projection texture . Input example: Output example: This example does the opposite with an equirectangular as source. If you look at the source of the above example: // mercator float latClamped = clamp(lat, -1.4835298641951802, 1.4835298641951802); float yMerc = log(tan(PI / 4.0 + latClamped / 2.0)) / PI2; float xMerc = xEqui / 2.0; vec4 mercatorPos = vec4(xMerc,

问题 I need to calculate an euclidean distance in a sqlite database. Does anyone know how to calculate square roots in sqlite beside writing and loading a dynamic library for math functions? I am close to resorting to the fast inverse square root algorithm in here http://en.wikipedia.org/wiki/Fast_inverse_square_root though it might to turn into more fun than I need right now. And as a side note, it'd be great to figure out how to do power (which is the generalized question, and is cleaner coding

问题 I'll preface with, this is solely to satisfy my curiosity rather than needing help on a coding project. But I was wanting to know if anyone knows of a function (particularly in python, but I'll accept a valid mathematical concept) kind of like absolute value, that given a number will return 0 if negative or return that number if positive. Pseudo code: def myFunc(x): if x > 0: return x else: return 0 Again, not asking the question out of complexity, just curiosity. I've needed it a couple

问题 I am writing a 3D collision, and want to know the difference in performance of basic math functions like + - * / sqrt pwr trigonometry like sin cos tan arcsin.. I heard it depends on many other things so I just want to get a rough idea about which one is slower and need to avoid while finding different ways to solve the problem. Also I want to know the order and the magnitude of the difference Thanks Edit: I write in VC++ for x86. But knowledge in other architectures and general picture are

问题 I'm trying to find the visible size of a sphere in pixels, after projection to screen space. The sphere is centered at the origin with the camera looking right at it. Thus the projected sphere should be a perfect circle in two dimensions. I am aware of this 1 existing question. However, the formula given there doesn't seem to produce the result I want. It is too small by a few percent. I assume this is because it is not correctly taking perspective into account. After projecting to screen

问题 I'm trying to find the visible size of a sphere in pixels, after projection to screen space. The sphere is centered at the origin with the camera looking right at it. Thus the projected sphere should be a perfect circle in two dimensions. I am aware of this 1 existing question. However, the formula given there doesn't seem to produce the result I want. It is too small by a few percent. I assume this is because it is not correctly taking perspective into account. After projecting to screen

问题 I am trying to use scipy.integrate.quad with Tensorflow as following. time and Lambda are two Tensors with shape (None, 1). def f_t(self, time, Lambda): h = Lambda * self.shape * time ** (self.shape - 1) S = tf.exp(-1 * Lambda * time ** self.shape) return h * S def left_censoring(self, time, Lambda): return tf.map_fn(lambda x: integrate.quad(self.f_t, 0.0, x[0], # it is not a float before evaluation args=(x[1],)), tf.concat([time, Lambda], 1)) However, I get an error as below: File "J:

问题 I am trying to convert a given double into scientific notation, and running into some problems. I cant seem to find much documentation on how to do it either. Currently I am using: var val = 500 var numberFormatter = NSNumberFormatter() numberFormatter.numberStyle = NSNumberFormatterStyle.ScientificStyle let number = numberFormatter.numberFromString("\(val)") println(number as Double?) // Prints optional(500) instead of optional(5e+2) What am I doing wrong? 回答1: You can set NumberFormatter