## 3 Results and Discussion
During the R peak localization process, missing R peaks were observed in normal sinus ECG recordings (no: 16,420 and 16,483) and arrhythmia ECG recordings (no: 101, 111, 121, 201, and 234). These missing peaks are highlighted in Figure 13 with a yellow circle. The missing peaks in the analysis were likely caused by selecting inappropriate values for the \"MinPeakDistance\" and \"MinPeakHeight\" parameters in the \"findpeaks\" MATLAB function or by data loss during the initial R peak localization process. These missing peaks lead to erroneous higher RR intervals. When a peak is missing, the gap between the neighboring R peaks increases, resulting in an incorrectly calculated maximum interval. Figure 14 shows the RR interval plots for recordings no. 16,420 and 121, highlighting the incorrect higher RR intervals due to these missing peaks. Figure 11: **(a)** Located R peaks. **(b)** RR interval vs. beat no. plot. **(c)** CWT spectrogram for the record: 117 using MODWPT. When comparing these plots with the MODWT method plots, we can observe a significant difference in the HF range until the 600 beat number. Figure 12: **(a)** Located R peaks. **(b)** RR interval vs. beat no. plot. **(c)** CWT spectrogram for record: 117 using MODWT. Adjusting the minimum distance and height of the R peaks did not resolve the issue and instead led to more incorrect higher RR intervals in the RR interval plots. It is important to note that reducing these parameters too much also caused incorrect R peak identification. For example, in Figure 13b, many peaks with higher amplitudes than the missing R peaks were identified, leading to incorrect R peak inclusion. After successfully locating R peaks, the RR intervals were calculated and plotted against the beat number. While some recordings showed incorrect higher intervals due to missing peaks, most recordings  
Figure 14: The RR interval plot of recording: (**a**) 16,420 observed with an incorrect higher interval between R peaks; (**b**) 16,420 obtained from the PhysioNet Database; (**c**) 121 observed with an incorrect higher interval between R peaks; (**d**) 121 obtained from the PhysioNet Database. Figure 13: Missing peaks observed in the R peaks plot of recording: (**a**) 16,420, (**b**) 16,483, (**c**) 101, (**d**) 111, (**e**) 121, and (**f**) 234. These plots show the missed R peak circled in yellow color. produced accurate RR interval plots. Figure 15 shows the RR interval plots for recordings no. 16,786 and 115, which resemble the reference plots from PhysioBank ATM. For ECG recordings no. 16,773 (Figure 16b) and 18,784, the reference RR interval plots from PhysioBank ATM displayed interruptions in the middle section, raising doubts about their accuracy. Consequently, these plots were considered incorrect. Figure 16: (a) RR interval plot of recording no. 16,773 plotted using MATLAB. (b) RR interval plot of recording no. 16,773 obtained from PhysioBank ATM. Figure 15: (a) RR interval plot of recording 16,786 plotted using MATLAB. (b) RR interval plot of recording 16,786 obtained from PhysioBank ATM. (c) RR interval plot of recording 230 plotted using MATLAB. (d) RR interval plot of recording 230 obtained from PhysioBank ATM. Out of 60 recordings, only 7 showed inaccurate RR interval plots, so the study proceeded to the next steps of plotting spectrograms and extracting frequency components. CWT was applied to the RR interval signal to obtain spectrograms, where amplitude (energy) is represented by three dimensions: frequency increases along the y-axis, with lower-frequency components at the bottom. The cone of influence indicates more accurate data inside and less accurate data outside. The focus was on the HF, LF, and VLF components (0.003 Hz to 0.4 Hz). High-magnitude events were observed in some spectrograms, like for recordings 19,093 and 228, but the study's main interest was analyzing HRV data through these frequency bands reflecting ANS activity.