I have a textfield called stateTextField. The purpose of this textField is for the user to enter in their state's abbreviation. (example: PA, CA, NH, ME)
When they type in the abbreviation, I want my app to realize it and assign it a decimal number for state income tax calculation purposes.
so this is what I have so far:
float netPay = grossPay * taxRate;
float stateTax = grossPay * stateRate;
float netPayState = netPay - stateTax;
float stateRate = [stateTextField.text floatValue];
if ([stateTextField.text isEqualToString:#"PA"] ||
[stateTextField.text isEqualToString:#".9693"])
However, I don't think this is going to work, am I going about this right? Please be polite, I am learning Objective C and this is new to me. Thank you :)
Fixed it with trial and error:
float PA = .0307;
float PATax = grossPay * PA;
if([self.stateTextField.text isEqual: #"PA"]) {
netPay = (grossPay - bonusRate) * taxRate - twoTaxes - PATax;
Related
Does anybody knows an algorithm for making a random series of numbers (like 100 java-byte (>=-127 & <= 127) ) which when are drawn as a bar chart, would be similar to a regular audio spectrum, like those SoundCloud ones?
I'm trying to write one, it has multiple Random and Sinus calculations, but the result is very ugly, it's something between a sinus wave and an old toothbrush. I would be very thankful if you code direct me to a one which is aesthetically convincing
An algorithm with an explanation (and/or picture) is fine. A pseudocode would be very nice of you. An actual JAVA code is bonus. :D
Edit:
This is the code I'm using right now. It's convoluted but I'm basically adding a random deviation to a sinus wave with random amplitude (which I'm not sure if it was a good idea).
private static final int FREQ = 7;
private static final double DEG_TO_RAD = Math.PI / 180;
private static final int MAX_AMPLITUDE = 127;
private static final float DEVIATION = 0.1f; // 10 percent is maximum deviation
private void makeSinusoidRandomBytes() {
byte[] bytes = new byte[AUDIO_VISUALIZER_DENSITY];
for (int i = 0; i < AUDIO_VISUALIZER_DENSITY; i++) {
int amplitude = random.nextInt(MAX_AMPLITUDE) - MAX_AMPLITUDE/2;
byte dev = (byte) (random.nextInt((int) Math.max(Math.abs(2 * DEVIATION * amplitude), 1))
- Math.abs(DEVIATION * amplitude));
bytes[i] = (byte) (Math.sin(i * FREQ * DEG_TO_RAD) * amplitude - dev);
}
this.bytes = bytes;
}
A real soundwave is actually a combination of sine waves of different frequencies and amplitudes added together, not random deviations from a sine wave. The difficult part will be to choose a combination of wave amplitudes and frequencies that will produce the output that you will subjectively like! However, most sound waves have a base frequency and then a number of overtones which "fit into" that wavelength - for example it might have an overtone at 3/2 * the base frequency and at amplitude of 2/3 the base frequency. By combining these overtones and scaling the resulting waveform to the -127 - +127 range, you'll get an actual soundwave.
The following code is C#, but close enough to Java to give you an idea. It's from a game, where I needed to combine many sine waves together to create various types of oscillating effects:
/// <summary>
/// Return a value between 0 and 1 based on a sine-wave oscillating with a given combination of periods at a given point in time
/// </summary>
/// <param name="time">time to get wave value at</param>
/// <param name="periods">lengths of waves</param>
/// <returns>height of wave</returns>
public static float MultiPulse(float time, params float[] periods)
{
float c = 0;
foreach (float p in periods)
{
float cp = (MathHelper.Pi / p) * time;
float s = ((float)Math.Sin(cp) + 1) / 2;
c += s / periods.Length;
}
return c;
}
You probably want to modify that to allow you to specify different amplitudes as well as periods for the waves you are combining.
By combining many widely varying amplitudes and periods (frequencies) you should by trial and error be able to get something convincing.
Based on the idea see sharper gave me, this is the code I'm using right now:
int mainAmp = random.nextInt(MAX_AMPLITUDE) - MAX_AMPLITUDE / 2;
int overtoneAmp = random.nextInt(MAX_AMPLITUDE * 2 / 3) - MAX_AMPLITUDE / 3;
int overtone2Amp = random.nextInt(MAX_AMPLITUDE * 4 / 7) - MAX_AMPLITUDE / 2 * 7;
int mainFreq = random.nextInt(7) + 7;
int overtoneFreq = mainFreq * 3 / 2;
int overtone2Freq = mainFreq * 7 / 4;
byte[] bytes = new byte[AUDIO_VISUALIZER_DENSITY];
for (int i = 0; i < AUDIO_VISUALIZER_DENSITY; i++) {
bytes[i] = (byte) (Math.sin(i * mainFreq * DEG_TO_RAD) * mainAmp
+ Math.sin(i * overtoneFreq * DEG_TO_RAD) * overtoneAmp
+ Math.sin(i * overtone2Freq * DEG_TO_RAD) * overtone2Amp);
}
Main frequency is between 8 and 15 for my app. You can play with those. The other two overtones I'm using are (2 - 1/2)x & (2 - 1/4)x of main frequency. You can add more like (2 - 1/8)x etc. Or use another series of frequencies. I also randomize the amplitude to get a unique wave each time.
These are some waves I'm drawing using this code:
I have the following class which generates a buffer containing sound data:
package musicbox.example;
import javax.sound.sampled.LineUnavailableException;
import musicbox.engine.SoundPlayer;
public class CChordTest {
private static final int SAMPLE_RATE = 1024 * 64;
private static final double PI2 = 2 * Math.PI;
/*
* Note frequencies in Hz.
*/
private static final double C4 = 261.626;
private static final double E4 = 329.628;
private static final double G4 = 391.995;
/**
* Returns buffer containing audio information representing the C chord
* played for the specified duration.
*
* #param duration The duration in milliseconds.
* #return Array of bytes representing the audio information.
*/
private static byte[] generateSoundBuffer(int duration) {
double durationInSeconds = duration / 1000.0;
int samples = (int) durationInSeconds * SAMPLE_RATE;
byte[] out = new byte[samples];
for (int i = 0; i < samples; i++) {
double value = 0.0;
double t = (i * durationInSeconds) / samples;
value += Math.sin(t * C4 * PI2); // C note
value += Math.sin(t * E4 * PI2); // E note
value += Math.sin(t * G4 * PI2); // G note
out[i] = (byte) (value * Byte.MAX_VALUE);
}
return out;
}
public static void main(String... args) throws LineUnavailableException {
SoundPlayer player = new SoundPlayer(SAMPLE_RATE);
player.play(generateSoundBuffer(1000));
}
}
Perhaps I'm misunderstanding some physics or math here, but it seems like each sinusoid ought to represent the sound of each note (C, E, and G), and by summing the three sinusoids, I should hear something similar to when I play those three notes simultaneously on the keyboard. What I'm hearing, however, is not even close to that.
For what it's worth, if I comment out any two of the sinusoids and keep the third, I do hear the (correct) note corresponding to that sinusoid.
Can somebody spot what I'm doing wrong?
To combine audio signals you need to average their samples, not sum them.
Divide the value by 3 before converting to byte.
You don't say in what way it sounds incorrect, adding three sin values like that you are going to get a signal that ranges from -3.0 to 3.0 and so is going to clip when you apply your *Byte.MAX_VALUE, this is why averaging probable worked for you, adding is correct its just you need to scale the result after to prevent clipping and dividing by the number of sine waves is the easiest way to do this. But if you start changing the number of sine waves dynamically and try to use the same strategy you wont get the result you expect, you have to scale the signal for when you signal is at its loudest. Remember real audio is not going to be at maximum amplitude so you don't have to worry about it two much if you synthesised audio isn't, also, the way we perceive sound volume is logarithmic so a signal at half amplitude is a difference of -3dB which is pretty close to the smallest change in amplitude we can hear.
I have a robotic arm composed of 2 servo motors. I am trying to calculate inverse kinematics such that the arm is positioned in the middle of a canvas and can move to all possible points in both directions (left and right). This is an image of the system Image. The first servo moves 0-180 (Anti-clockwise). The second servo moves 0-180 (clockwise).
Here is my code:
int L1 = 170;
int L2 = 230;
Vector shoulderV;
Vector targetV;
shoulderV = new Vector(0,0);
targetV = new Vector(0,400);
Vector difference = Vector.Subtract(targetV, shoulderV);
double L3 = difference.Length;
if (L3 > 400) { L3 = 400; }
if (L3 < 170) { L3 = 170; }
// a + b is the equivelant of the shoulder angle
double a = Math.Acos((L1 * L1 + L3 * L3 - L2 * L2) / (2 * L1 * L3));
double b = Math.Atan(difference.Y / difference.X);
// S1 is the shoulder angle
double S1 = a + b;
// S2 is the elbow angle
double S2 = Math.Acos((L1 * L1 + L2 * L2 - L3 * L3) / (2 * L1 * L2));
int shoulderAngle = Convert.ToInt16(Math.Round(S1 * 180 / Math.PI));
if (shoulderAngle < 0) { shoulderAngle = 180 - shoulderAngle; }
if (shoulderAngle > 180) { shoulderAngle = 180; }
int elbowAngle = Convert.ToInt16(Math.Round(S2 * 180 / Math.PI));
elbowAngle = 180 - elbowAngle;
Initially, when the system is first started, the arm is straightened with shoulder=90, elbow =0.
When I give positive x values I get correct results in the left side of the canvas. However, I want the arm to move in the right side as well. I do not get correct values when I enter negatives. What am I doing wrong? Do I need an extra servo to reach points in the right side?
Sorry if the explanation is not good. English is not my first language.
I suspect that you are losing a sign when you are using Math.Atan(). I don't know what programming language or environment this is, but try and see if you have something like this:
Instead of this line:
double b = Math.Atan(difference.Y / difference.X);
Use something like this:
double b = Math.Atan2(difference.Y, difference.X);
When difference.Y and difference.X have the same sign, dividing them results in a positive value. That prevents you from differentiating between the cases when they are both positive and both negative. In that case, you cannot differentiate between 30 and 210 degrees, for example.
Here's the link to the question..
http://www.codechef.com/problems/J7
I figured out that 2 edges have to be equal in order to give the maximum volume, and then used x, x, a*x as the lengths of the three edges to write the equations -
4*x + 4*x + 4*a*x = P (perimeter) and,
2*x^2 + 4*(a*x *x) = S (total area of the box)
so from the first equation I got x in terms of P and a, and then substituted it in the second equation and then got a quadratic equation with the unknown being a. and then I used the greater root of a and got x.
But this method seems to be giving the wrong answer! :|
I know that there isn't any logical error in this. Maybe some formatting error?
Here's the main code that I've written :
{
public static void main(String[] args)
{
TheBestBox box = new TheBestBox();
reader = box.new InputReader(System.in);
writer = box.new OutputWriter(System.out);
getAttributes();
writer.flush();
reader.close();
writer.close();
}
public static void getAttributes()
{
t = reader.nextInt(); // t is the number of test cases in the question
for (int i = 0; i < t; i++)
{
p = reader.nextInt(); // p is the perimeter given as input
area = reader.nextInt(); // area of the whole sheet, given as input
a = findRoot(); // the fraction by which the third side differs by the first two
side = (double) p / (4 * (2 + a)); // length of the first and the second sides (equal)
height = a * side; // assuming that the base is a square, the height has to be the side which differs from the other two
// writer.println(side * side * height);
// System.out.printf("%.2f\n", (side * side * height));
writer.println(String.format("%.2f", (side * side * height))); // just printing out the final answer
}
}
public static double findRoot() // the method to find the 2 possible fractions by which the height can differ from the other two sides and return the bigger one of them
{
double a32, b, discriminant, root1, root2;
a32 = 32 * area - p * p;
b = 32 * area - 2 * p * p;
discriminant = Math.sqrt(b * b - 4 * 8 * area * a32);
double temp;
temp = 2 * 8 * area;
root1 = (- b + discriminant) / temp;
root2 = (- b - discriminant) / temp;
return Math.max(root1, root2);
}
}
could someone please help me out with this? Thank You. :)
I also got stuck in this question and realized that can be done by making equation of V(volume) in terms of one side say 'l' and using differentiation to find maximum volume in terms of any one side 'l'.
So, equations are like this :-
P = 4(l+b+h);
S = 2(l*b+b*h+l*h);
V = l*b*h;
so equation in l for V = (l^3) - (l^2)P/4 + lS/2 -------equ(1)
After differentiation we get:-
d(V)/d(l) = 3*(l^2) - l*P/2 + S/2;
to get max V we need to equate above equation to zero(0) and get the value of l.
So, solutions to a quadratic equation will be:-
l = ( P + sqrt((P^2)-24S) ) / 24;
so substitute this l in equation(1) to get max volume.
I'm moving my SQLite database over to Core Data. My database table looks like this:
CREATE TABLE IF NOT EXISTS stops (id integer primary key autoincrement, type text, lat real, lon real, stop_id integer unique, stop_code integer, title text, subtitle text, url text, lastupdate text
My Entity looks like this:
I'm not worries about moving the data over, it's really just a local cache that gets updated from time to time. If its empty, it will just repopulate.
My issue is I have a SQLite custom function:
static void distanceFunc(sqlite3_context *context, int argc, sqlite3_value **argv)
{
// check that we have four arguments (lat1, lon1, lat2, lon2)
assert(argc == 4);
// check that all four arguments are non-null
if (sqlite3_value_type(argv[0]) == SQLITE_NULL || sqlite3_value_type(argv[1]) == SQLITE_NULL || sqlite3_value_type(argv[2]) == SQLITE_NULL || sqlite3_value_type(argv[3]) == SQLITE_NULL) {
sqlite3_result_null(context);
return;
}
// get the four argument values
double lat1 = sqlite3_value_double(argv[0]);
double lon1 = sqlite3_value_double(argv[1]);
double lat2 = sqlite3_value_double(argv[2]);
double lon2 = sqlite3_value_double(argv[3]);
// convert lat1 and lat2 into radians now, to avoid doing it twice below
double lat1rad = DEG2RAD(lat1);
double lat2rad = DEG2RAD(lat2);
// apply the spherical law of cosines to our latitudes and longitudes, and set the result appropriately
// 6378.1 is the approximate radius of the earth in kilometres
sqlite3_result_double(context, acos(sin(lat1rad) * sin(lat2rad) + cos(lat1rad) * cos(lat2rad) * cos(DEG2RAD(lon2) - DEG2RAD(lon1))) * 6378.1);
}
The function given a 2 latitudes and 2 longitudes would return the distance. This would let me do something like:
SELECT *, distance(lat, lon, %f, %f) as dist FROM stops WHERE dist < 1 ORDER BY dist
Now, I've got all my data in Core Data, but no idea how to do something like the SQL above with a NSFetchRequest. So how would I go about fetching entities in this manner?