Biomedical Data Mining for Information Retrieval. Группа авторов

1.2.

      From these 15 variables, first value, last value, highest value, lowest value and median value are calculated for nine variables and taken as features. Only first and last values are taken for four variables. For the dataset A, five outcome-related descriptors (SAPS Score, SOFA Score, length of stay, length of survival and in-hospital death) are available from which inhospital death (0 is represented as a survivor and 1 is represented as died in hospital) is taken as a target value.

      1.3.2 Data Pre-Processing

      Data pre-processing is one of the technique to filter and remove noisy data. 41 variables are given in the dataset. Among them 15 variables are selected out of which some of the variables are not carefully collected and having missing values. In this chapter, missing data are replaced by zeros.

      1.3.3 Normalization

      All the variables in the dataset are in different ranges and in different scales. The current values of data cannot be used for classification. If all the variables have the values in better ranges and scales, classifiers will work in a better way. A standard approach, z-score normalization method is used to normalize the variables.

Table 1.1 Time series variables with description and physical units recorded in the ICU [6].

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S. no.	Variables	Description	Physical units
1.	Albumin	Albumin	g/dL
2.	ALP	Alkaline Phosphate	IU/L
3.	ALT	Alanine transaminase	IU/L
4.	AST	Aspartate transaminase	IU/L
5.	Bilirubin	Bilirubin	mg/dL
6.	BUN	Blood urea nitrogen	mg/dL
7.	Cholesterol	Cholesterol	mg/dL
8.	Creatinine	Creatinine	mg/dL
9.	DiasABP	Invasive diastolic arterial blood pressure	mmHg
10.	FiO2	Fractional inspired oxygen	[0–1]
11.	GCS	Glasgow Coma Score	[3–15]
12.	Glucose	Serum Glucose	mg/dL
13.	HCO3	Serum Bicarbonate	mmol/L
14.	HCT	Hematocrit	%
15.	HR	Heart Rate	bpm
16.	K	Serum Potassium	mEq/L
17.	Lactate	Lactate	mmol/L
18.	Mg	Serum Magnesium	mmol/L
19.	MAP	Invasive mean arterial blood pressure	mmHg
20.	MechVent	Mechanical Respiration Ventilation	0/1(true/false)
21.	Na	Serum Sodium	mEq/L
22.	NIDiasABP	Non-invasive diastolic arterial blood pressure	mmHg
23.	NIMAP	Non-invasive mean arterial blood pressure	mmHg
24.	NISysABP	Non-invasive systolic arterial blood pressure	mmHg
25.	PaCO2	Partial pressure of arterial carbon dioxide	mmHg
26.	PaO2	Partial pressure of arterial oxygen	mmHg
27.	pH	Arterial pH	[0–14]
28.	Platelets	Platelets	cells/nL
29.	RespRate	Respiration Rate	bpm
30.	SaO2	O2 saturation in hemoglobin	%
31.	SysABP	Invasive systolic arterial blood pressure	mmHg
32.	Temp	Temperature	°C