I attempted to create a variable named "Besoin_fr"to store results in it, using another variable that is unnecessary. I tried to assign the calculations of the second variable to the old named " conso_eau_z1". Knowing that it is a Shiny application and it returns the results in the form of an Excel table, with each column corresponding to the results of a calculated variable.
> Besoin <- m_mel * (Caract_melangeh - h3)
> Besoin_fr<-Besoin
Creation of a vector Besoin_fr to store the values of Besoin_fr 
besoin_fr<-numeric(nombre_de_pas)
Calling the function that returns the results ofBesoin_fr
Resultats = Fct_traitement_vapeur (Matrice_soufflage["C","Temp"], Matrice_soufflage["C","r"], T_adp, r_adp, Caract_melange$r, Caract_melange$Temp,
Matrice_soufflage["D","r"], Matrice_soufflage["D","Temp"], Caract_melange$h, Matrice_soufflage["B","h"], Matrice_soufflage["B","r"],
Besoin, m_mel, zone, P_e_ch, Besc, Besf, T_s_e_ch, T_e_e_ch, m_e_ch, rend_batterie, eff_humid, Matrice_soufflage["B","Temp"],
m_eau_conso, m_eau_conso_z1, m_eau_cond, conso_humid, Matrice_soufflage["A","r"], Caract_melange$HR, Matrice_soufflage["A","HR"],
Matrice_soufflage["C","h"], Matrice_soufflage["B","HR"], P_e_fr, h_adp, m_e_fr, T_s_e_fr, T_e_e_fr,Besoin_fr )
m_eau_conso_z1 = Resultats$Besoin_fr ##Assigning the results
conso_eau_z1_hist[[i]] <-Besoin_fr ## storing the values of Besoin_fr
paste("Besoin de froid zone8 (Besoin_fr [kWh])"), ##in server function replace the name of a column in a data frame
please help mee to solve this problem