Unexpected Extreme Values in scPDSI and PDSI Calculations

[gingerlolipop]

I'm encountering very high (e.g., Inf) and very low (e.g., < -2000) values in both scPDSI and conventional PDSI calculations using the scPDSI package.

Below I selected two pixels of my drought-mapping area as examples. One results in abnormal scPDSI value, and the other results in (not self calibrated) PDSI values:

# Example 1 - scPDSI values abnormal, PDSI values normal
p_vector_1 <- c(229, 181, 21, 15, 192, 84, 55, 113, 199, 521, 328, 165, 606, 40, 14, 27, 83, 106, 63, 229, 95, 432, 382, 182, 99, 234, 28, 25, 43, 73, 132, 118, 209, 213, 392, 142, 287, 127, 44, 22, 134, 125, 194, 233, 229, 305, 382, 112, 440, 157, 11, 41, 102, 33, 85, 106, 152, 626, 255, 108)
pe_vector_1 <- c(12, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 11, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 11, 12, 19, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 12, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001)

scpdsi_values_1 <- scPDSI::pdsi(P = p_vector_1, PE = pe_vector_1, AWC = 113, start = 1961, sc = TRUE)$X
pdsi_values_1 <- scPDSI::pdsi(P = p_vector_1, PE = pe_vector_1, AWC = 113, start = 1961, sc = FALSE)$X



# Example 2 - scPDSI values normal, PDSI values abnormal
p_vector_2 <- c(792, 997, 336, 207, 259, 147, 29, 248, 594, 1136, 1144, 1108, 2012, 148, 184, 342, 88, 176, 37, 386, 325, 853, 1404, 1227, 378, 1161, 386, 304, 59, 135, 91, 126, 656, 504, 1238, 1254, 899, 739, 663, 363, 179, 189, 139, 335, 756, 625, 1052, 777, 1355, 968, 154, 466, 155, 66, 63, 150, 534, 1194, 683, 922)
pe_vector_2 <- c(0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001)

scpdsi_values_2 <- scPDSI::pdsi(P = p_vector_2, PE = pe_vector_2, AWC = 113, start = 1961, sc = TRUE)$X
pdsi_values_2 <- scPDSI::pdsi(P = p_vector_2, PE = pe_vector_2, AWC = 113, start = 1961, sc = FALSE)$X

The p vectors are precipitation (mm), and the pe vectors are evapotranspiration (mm). I replaced 0 values as 0.0001. Could you please advise on whether this is expected or if there might be a bug in the package? Any guidance on handling such cases would be greatly appreciated!