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Numeric error propagation: Difference between revisions
+Java
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<lang j> exp&0.5 (x1 sub x2) add&(exp&2) y1 sub y2
111.803 2.48717</lang>
=={{header|Java}}==
<lang java>public class Approx {
private double value;
private double error;
public Approx(){this.value = this.error = 0;}
public Approx(Approx b){
this.value = b.value;
this.error = b.error;
}
public Approx(double value, double error){
this.value = value;
this.error = error;
}
public Approx add(Approx b){
value+= b.value;
error = Math.sqrt(error * error + b.error * b.error);
return this;
}
public Approx add(double b){
value+= b;
return this;
}
public Approx sub(Approx b){
value-= b.value;
error = Math.sqrt(error * error + b.error * b.error);
return this;
}
public Approx sub(double b){
value-= b;
return this;
}
public Approx mult(Approx b){
double oldVal = value;
value*= b.value;
error = Math.sqrt(value * value * (error*error) / (oldVal*oldVal) +
(b.error*b.error) / (b.value*b.value));
return this;
}
public Approx mult(double b){
value*= b;
error = Math.abs(b * error);
return this;
}
public Approx div(Approx b){
double oldVal = value;
value/= b.value;
error = Math.sqrt(value * value * (error*error) / (oldVal*oldVal) +
(b.error*b.error) / (b.value*b.value));
return this;
}
public Approx div(double b){
value/= b;
error = Math.abs(b * error);
return this;
}
public Approx pow(double b){
double oldVal = value;
value = Math.pow(value, b);
error = Math.abs(value * b * (error / oldVal));
return this;
}
@Override
public String toString(){return value+"±"+error;}
public static void main(String[] args){
Approx x1 = new Approx(100, 1.1);
Approx x2 = new Approx(50, 1.2);
Approx y1 = new Approx(200, 2.2);
Approx y2 = new Approx(100, 2.3);
x1.sub(x2).pow(2).add(y1.sub(y2).pow(2)).pow(0.5);
System.out.println(x1);
}
}</lang>
Output:
<pre>111.80339887498948±2.938366893361004</pre>
=={{header|Mathematica}}==
<lang mathematica>PlusMinus /: a_ ± σa_ + c_?NumericQ := N[(a + c) ± σa];
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