From a9e67d9857160aa0932f05c85a60eb10c95e36fa Mon Sep 17 00:00:00 2001
From: uhensler <urs.hensler@frentix.com>
Date: Tue, 18 Jun 2019 11:11:31 +0200
Subject: [PATCH] OO-4100: Calculation of variance / standard deviation in
survey reports
---
.../forms/model/jpa/RubricStatisticImpl.java | 31 ++++++-------------
1 file changed, 10 insertions(+), 21 deletions(-)
diff --git a/src/main/java/org/olat/modules/forms/model/jpa/RubricStatisticImpl.java b/src/main/java/org/olat/modules/forms/model/jpa/RubricStatisticImpl.java
index 612fe901e14..393dcb1e427 100644
--- a/src/main/java/org/olat/modules/forms/model/jpa/RubricStatisticImpl.java
+++ b/src/main/java/org/olat/modules/forms/model/jpa/RubricStatisticImpl.java
@@ -178,13 +178,17 @@ public class RubricStatisticImpl implements RubricStatistic {
Double mean = getAverage(stepCounts);
if (mean == null) return null;
- List<Double> scaledValues = getScaledValues(stepCounts);
- if (scaledValues.size() < 2) return null;
-
double temp = 0;
- for(double a: scaledValues)
- temp += (a-mean)*(a-mean);
- return temp/(scaledValues.size() - 1);
+ int size = 0;
+ for (int step = 1; step <= rubric.getSteps(); step++) {
+ double value = rubric.getScaleType().getStepValue(rubric.getSteps(), step);
+ int count = stepCounts.get(step - 1).intValue();
+ for (int i = 0; i < count; i++) {
+ temp += (value-mean)*(value-mean);
+ size++;
+ }
+ }
+ return size > 2? temp/(size - 1): null;
}
private Double getStdDev(List<Long> stepCounts) {
@@ -194,21 +198,6 @@ public class RubricStatisticImpl implements RubricStatistic {
return Math.sqrt(getVariance(stepCounts));
}
- private List<Double> getScaledValues(List<Long> stepCounts) {
- List<Double> scaledValues = new ArrayList<>();
- for (int step = 1; step <= rubric.getSteps(); step++) {
- Long count = stepCounts.get(step - 1);
- if (count != null) {
- double stepValue = rubric.getScaleType().getStepValue(rubric.getSteps(), step);
- for (int i = 0; i < count; i++) {
- double scaledValue = stepValue * step;
- scaledValues.add(Double.valueOf(scaledValue));
- }
- }
- }
- return scaledValues;
- }
-
private void calculateTotalStatistics() {
Long numberOfNoResponses = countedNoResponses.stream().mapToLong(CalculatedLong::getValue).sum();
List<Long> totalStepCounts = getTotalStepCounts();
--
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