apop_plot_query: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/bin/apop_plot_query - from package: apophenia-bin

You may install the required package with command apt-get install {package}

Error in other languages:
apop_plot_query: bevel nie gevind nie
apop_plot_query: comandă negăsită
apop_plot_query: comando não encontrado
apop_plot_query: commande introuvable
apop_plot_query: command not found
apop_plot_query: käsku ei ole
apop_plot_query: không tìm thấy lệnh
apop_plot_query: komanda nerasta
apop_plot_query: Kommando nicht gefunden.
apop_plot_query: kommandot finns inte
apop_plot_query: komut yok
apop_plot_query: nie znaleziono polecenia
apop_plot_query: níor aimsíodh an t-ordú
apop_plot_query: no se encontró la orden
apop_plot_query: no s'ha trobat l'ordre
apop_plot_query: opdracht niet gevonden
apop_plot_query: parancs nem található
apop_plot_query: perintah tidak ditemukan
apop_plot_query: príkaz nenájdený
apop_plot_query: příkaz nenalezen
apop_plot_query: команда не найдена
apop_plot_query: командата не е открита
apop_plot_query: 命令找不到
apop_plot_query: コマンドが見つかりません