How to find x and y of a point of a mathematical function in Rstudio ..?

[Yarnabrina]

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However, please note that if this is your actual code, you once again omitted the * in these two lines:

A2 <- function(f) abs(1/(cos(2 pi f H (1-1i*D)/Vs)))

and

VettoreMassimo[k]=abs(1/(cos(2 pi j H*(1-1i*D)/Vs)))

Also, let me give you a better way for this problem. You actually don't need the for loop here:

# Funzione di amplificazione A2
H <- 10 # [m] Spessore strato
Vs <- 200 # [m/s] Velocità onde S
D <- 0.05 # [%] Smorzamento

# Funzione di amplificazione A2
A2 <- function(f) abs(x = (1/(cos(2 * pi *f * H * (1 - 1i * D) / Vs))))

# Calcolo massimo
N <- seq(from = 0, to = 100, by = 0.001)
VettoreMassimo <- A2(f = N)
m <- max(VettoreMassimo)
f0 <- N[which.max(x = VettoreMassimo)]

# Stampa risultati
cat("Valore massimo di A2:", m)
#> Valore massimo di A2: 12.73528
cat("Frequenza fondamentale f0:", f0)
#> Frequenza fondamentale f0: 4.987

^{Created on 2019-02-23 by the reprex package (v0.2.1)}