  Heart rate variability,important marker for modulation of autonomic nervous
system is studied for diabetic,hypertensive and control group of
subjects.Lagged Poincar\'{e} plot of heart rate(HR),method of principal
component analysis and auto-correlation of HR fluctuation are used to analyze
HR obtained from ECG signal recorded over short time duration.The parameters
$(SD1)$,$(SD2)$ and their ratio $(SD12)$,characterizing the Poincar\'{e} plot
reveal a significant reduction of their values for diabetic and hypertensive
subjects compared to the corresponding results of control one.The slope and the
curvature of the plot of these parameters with lagged number exhibit similar
trend.In particular,the curvature of $(SD12)$ for the control group differs
widely from that of other groups.The principal component analysis is used for
analysing multi-dimensional data set resulting from the Poincar\'{e} plot for
all subjects.The correlation matrix points out significant correlation between
slope and curvature.The analysis demonstrates that three groups are well
separated in the domain of two significant principal components.The
auto-correlation of HR fluctuation exhibits highly correlated pattern for
subjects with health disorder compared to that of control subject.
